CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application Serial No. 60/240,596 filed on Oct. 13, 2000 the entirety of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1 . Field of Invention

The invention relates to methods and systems for performing stress testing of equipment. The invention also relates to active and passive stress testing using modular design and robust data collection that is adaptable to a variety of equipment.

2 . Description of Related Art

It is common to subject integrated circuits (IC) to various stresses to ensure reliability. Specifically, an IC is typically subjected to high temperatures for an extended period of time. This process is called “bum-in” testing in the art and identifies marginal devices likely to succumb to such stresses in the field.

Various systems and methods have been designed to perform burn-in testing of integrated circuits and computer components. Many of these conventional solutions focus on specific adapters and hardware that permit high-volume bum-in testing of specific equipment.

For example, Slocum (U.S Pat. No. 6,097,201) discloses a system of stackable test boards in which a large number of integrated circuit boards may be mounted. Each of Slocum's test boards includes a contactor region that permits test signals to be routed to the individual integrated circuit boards. As such, Slocum's system is specifically designed to perform high-volume burn-in testing of specific components (integrated circuit boards).

Leung (U.S. Pat. No. 5,798,653) utilizes a special-purpose burn-in controller located within the burn-in oven to “exercise” an integrated circuit (IC) by toggling a high percentage of the switches within the IC.

Leung also illustrates the conventional thinking of burn-in testing which is to select a statistically significant sample of the product (IC's in this case) which are then subjected to burn-in testing. Like Slocum, Leung's system performs a dynamic test in which input stimuli are applied to the ICs to exercise or toggle the electrical circuit nodes of the IC.

Leung performs two types of dynamic burn-in testing on these sample IC's including an infant mortality burn-in and a longevity qualifying burn-in which mainly differ in the amount of time in which the IC's are subjected to the age-accelerating burn-in test. A simple data set is collected from these tests, which includes how many ICs succumb to infant mortality.

The flexibility of conventional stress testing systems is quite limited. Moreover, the number testing circuits matches the number of IC boards being tested thus requiring duplicative testing hardware. Moreover, the data collected by conventional system is quite rudimentary. Thus, there is a need in the art that solves these and other deficiencies in conventional stress-testing systems.

SUMMARY OF THE INVENTION

The present invention brings revolutionary concepts to the field of stress testing: utilizing a virtual oven, sharing test equipment, and logically grouping components and modules to be tested provides many distinct advantages over the prior art.

In general, the inventive systems and methods solve the problem of massive manual management of the following: a) process control, b) data, c) active signal controls, and d) product performance verification for stress testing. This goal was accomplished by designing, developing, and making operational an Automated Monitoring System (AMS). AMS communicates to modules and test equipment that are undergoing and performing stress testing as well as collecting the data automatically.

Stress testing according to one aspect of the invention includes exposing operating equipment/modules to thermal stress (or other stressor(s)) over a long (e.g. 48 hour) period of time including an (e.g. 24 hour) active test such as a bit error rate test (BERT) for optically tested modules (e.g. transmitters, receivers, remodulators, selectors, transceivers, variable optical attenuators, and amplifiers). The stress tests may also involve introducing noise to the test signal and/or degrading the test signal strength. The invention is capable of testing a wide variety of other components including electronic, opto-electronic, and optical components.

The inventive stress-testing process is a critical component of the manufacturing flow for producing reliable modules because the invention:

Reveals module damage due to handling (e.g. electrostatic discharge or other handling related damage).

Virtually simulates field conditions over a broad range of temperatures, operating conditions, and signal conditions.

Deliberately ages the product so as to eliminate substantially all early life failures from the product shipped to the customer.

More specifically, virtual oven for stress testing a plurality of modules includes a logical group of modules loaded into an environmental stress screening room wherein an environmental stress parameter of the environmental stress screening room changes over time; a test equipment operatively connected to the modules of said logical group, said test equipment generating a test signal and capable of performing an active test of at least one of the modules of said logical group at a time; and a controller operatively connected to said test equipment and to said logical group of modules; said controller receiving results of the active test performed by said test equipment.

The modules may also include sensors or other devices for measuring parameters of the module and the controller may receive passive test measurement values from these sensors. In this way, a passive test of the modules may be performed independently of and simultaneous with the active testing. The results of the active test and the passive test measurement values for each of the modules are associated with the module and stored in a database.

Furthermore, the controller may send a command to at least one module of the logical group to, for example, place that module in a desired operational state, exercise the module, or otherwise assist in the testing regime.

Moreover, a network may be used to operatively connect the test equipment with the controller, the memory device, and each of the modules of the logical group. The invention also includes a system of virtual ovens that may be connected via a network.

The inventive methods for stress-testing a plurality of modules includes designating a logical group of modules in an environmental stress screening room wherein an environmental stress parameter of the environmental stress screening room changes over time; generating a test signal; supplying the test signal to at least one of the modules of the logical group to subject the at least one module to an active test thereof, and receiving results of the active test from one of the modules of the logical group with a test equipment.

The method may perform a series of tests of the logical group modules on a time-share basis with the test equipment. In addition, the method may further include receiving passive test measurement values from at least one of the modules of the logical group; analyzing the passive test measurement values and the active test results; and displaying results of said analyzing step.

Moreover, the invention encompasses a method of asynchronously conducting stress testing on a plurality of groups modules including a first and second logical groups of modules. This method asynchronously initiates testing of the first and second logical groups of modules; tests the first logical group of modules with the first test equipment; and tests the second logical group of modules with the second test equipment, wherein each of said testing steps respectively includes said generating step, said supplying step, and said receiving step.

The inventive methods also include receiving passive test measurement values from at least one of the modules of the logical group; and storing results of the active test and the passive test measurement values for each of the modules in the database.

Moreover, the modules comprising the logical groupings are not necessarily physically adjacent to one another.

The inventive virtual oven system may also utilize an inventive database. In particular, the database invention includes a stress-test information database stored in a computer-readable medium and usable for storing information related to a stress-test of different products, comprising: a product data entity storing product-specific information for a plurality of the different products that may be subjected to the stress-test; a process data entity storing testing process information for conducting one or more stress-test processes of the stress-test; a result data entity storing stress-test result information relating to one or more results of the stress-test processes; a product-result map relating said product data entity to said result data entity; and a process-result map relating said process data entity to said result data entity.

The stress-test information database may further include, particularly when a plurality of equipment is utilized to conduct the stress-test, the following elements: a command data entity storing command information that may be utilized to command the equipment; and an equipment data entity storing information relating to the equipment; said equipment data entity being associated with said command data entity to permit a variety of equipment-specific command information to be retrieved.

The command data entity may include a generic command data entity storing information relating to generic commands usable to conduct the stress test processes and an equipment command string data entity usable for translating generic commands to equipment-specific commands, said generic command data entity being associated with said equipment command string data entity; and said equipment data entity being associated with said command data entity, wherein a generic command may be translated into an equipment-specific command via the associations between said generic command data entity, said equipment command string data entity, and said equipment data entity.

In addition, the stress-test database may further include: a parsing table storing information relating to parsing of equipment-specific data received as a result of the stress test; said parsing table being associated with said equipment data entity to permit the equipment-specific data to be parsed into a more consistent format suitable for storage by said result data entity.

If the database is used with the virtual oven invention discussed above, it is advantageous to fither include a virtual oven data entity storing information relating to one or more virtual ovens that may be utilized to conduct the stress test. More particularly, the process data entity may include: a process information item storing information relating to stress test process identity and test process description; a process test run data entity storing information relating to stress test process identity, virtual oven identity and stress test process start/stop time(s); and a virtual oven data entity storing information relating to virtual oven identity, virtual oven description and virtual oven location, said process test run data entity relating said virtual oven data entity to said process information item in order to permit functional associations between virtual ovens, stress test processes, and process-test runs.

Moreover, the stress-test database may also include a test criteria data entity storing information relating to stress-test criteria, said test criteria data entity being associated with said result value data entity, said result value data entity item further including a pass/fail information item, said result value data entity and said test criteria data entity being usable to determine whether the product has passed or failed one or more of the stress-test processes.

In addition, an inventive method of storing information related to a stress-test of different products in a computer-readable stress-test information database is disclosed and includes: storing product-specific information for a plurality of the different products that may be subjected to the stress-test in a product data entity; storing testing process information for conducting one or more stress-test processes of the stress-test in a process data entity; storing stress-test result information relating to one or more results of the stress-test processes in a result data entity; relating the product data entity to the result data entity with a product-result map; and relating the process data entity to the result data entity with a process-result map.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1

a

is a block diagram of the virtual oven concept according to the invention showing logically grouped modules, the association of the test equipment with each logical group, and the arrangement of test equipment outside of an environmental stress screening room;

FIG. 1

b

is a block diagram of the virtual oven concept according to the invention showing logically grouped modules, the association of the test equipment with each logical group, and the arrangement of test equipment inside of an environmental stress screening room;

FIG. 2

is a conventional temperature profile showing how the temperature of the environmental stress screening room may be changed;

FIG. 3

is a block diagram showing switches that permit the test equipment to be time-shared among modules of a logical group;

FIG. 4

is a block diagram virtual ovens according to the invention in which the test instruments are connected to the modules via a network and in which plural virtual ovens are connected over the network to a database;

FIG. 5

is a block diagram showing operative connections within a virtual oven testing optical communications modules;

FIG. 6

a

is a block diagram showing alternative equipment and operative connections within a virtual oven testing optical communications modules;

FIG. 6

b

is a block diagram showing additional alternative operative connections within a virtual oven testing optical communications modules;

FIG. 6

c

is a block diagram showing operative connections within a virtual oven testing generalized modules;

FIG. 6

d

is a block diagram showing alternative equipment and operative connections within a virtual oven testing generalized modules;

FIG. 6

e

is a block diagram showing alternative equipment and operative connections within a virtual oven testing optical communications modules and capable of noise-loading and/or degrading the test signal strength;

FIG. 7

is a high-level block diagram showing an Internet-based architecture for connecting various components of the invention;

FIG. 8

is a flowchart showing details of a method of conducting burn-in testing according to the invention for two modules;

FIG. 9

is flowchart showing details of a method of conducting burn-in testing according to the invention for three or more modules;

FIG. 10

is a screen display of a graphical user interface according to the invention;

FIG. 11

is a high-level data relationship diagram illustrating the inventive database that may be used with the inventive systems and methods;

FIG. 12

is a mid-level data relationship diagram illustrating test equipment command and communication table details of the inventive database that may be used with the inventive systems and methods;

FIG. 13

is a mid-level data relationship diagram illustrating command table and test & equipment table details of the inventive database that may be used with the inventive systems and methods;

FIG. 14

is a mid-level data relationship diagram illustrating result table and process table details of the inventive database that may be used with the inventive systems and methods; and

FIG. 15

is a mid-level data relationship diagram illustrating product table and test criteria table details of the inventive database that may be used with the inventive systems and methods.

DETAILED DESCRIPTION OF INVENTION

The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents thereof.

As shown in

FIG. 1

a

, the inventive system

1

utilizes an environmental stress screening room (ESSR)

5

that is a conventional chamber having known heating and cooling equipment, thermocouples for measuring an internal temperature, and a temperature control unit. Such ESSR's are commercially available from a variety of companies. The ESSR

5

is typically controlled to change its internal temperature according to a predefined temperature profile such as the one shown in FIG.

2

.

Although the invention is primarily intended to subject modules

15

to a temperature profile, the ESSR

5

is not limited to merely changing its internal temperature. Indeed, any form of environmental stress parameter such as humidity, radiation, vibration or a combination thereof may be used to stress the modules

15

under test. The invention is also capable of introducing noise into the test signal and/or degrading the test signal strength to apply other forms of stress to the modules

15

under test.

FIG. 1

a

illustrates the logical grouping

30

that is a key aspect of the virtual oven

10

. Conventional burn-in systems require modules being tested to be physically adjacent. A logical grouping

30

of modules groups modules

30

that are not necessarily physically adjacent. For example, different equipment racks can be used to hold the modules of a logical group while they undergo bum-in testing.

Also, an equipment rack may be partially loaded with modules and each module loaded in the partially filled rack designated as a logical group

30

by the inventive software. When the equipment rack is then filled, those modules may form another logical group

30

. Such logical grouping

30

permits the invention to be highly modular and adaptive to the manufacturing environment.

The ESSR

5

may include one or more virtual ovens

10

, but preferably there is more than one virtual oven

10

per ESSR

5

as shown in

FIGS. 1

a

and

1

b

. Each virtual oven includes one or more logical groups

30

of modules

15

and associated test equipment

25

.

In practice, the virtual oven will include a large number of logical groups

30

but at a minimum each virtual oven will include at least one logical group

30

. The number of modules

15

within each logical group

30

may also vary but a typical number is two to eight modules

15

per logical group.

Furthermore, each logical group

30

within the virtual oven

10

includes an associated clock or timer

12

that is started after the logical group

30

of modules

15

is loaded into the ESSR

5

and when the testing of that logical group

30

begins.

The virtual oven

10

logical module grouping concept and associated control permits the invention to be highly modular and adaptive to the manufacturing production line feeding modules

15

to the burn-in system

1

. Conventional systems typically load a large batch of modules into an oven, attach test equipment to each module and gather data from the modules as they are being tested. If only a few modules are completed, then only a small portion of the oven would be utilized to conduct the burn-in test with a corresponding gross reduction in oven throughput and efficiency. In other words, the conventional bum-in systems do not permit asynchronous loading and test starting of an arbitrary number of modules.

In contrast, each logical group

30

of each virtual oven

10

provides a modular platform for loading and testing an arbitrary number of modules

15

. As batches of modules

15

are completed, the logical groups

30

may be loaded and a corresponding bum-in test started. When the next batch of modules

15

is completed another logical group

30

within the same or a different virtual oven

10

can be loaded and another bum-in test started.

FIG. 1

b

further extends the virtual oven

10

concept. As shown in

FIG. 1

b

, all or most of the equipment for a virtual oven

10

can be physically located within the environmental stress screening room

5

. Particularly, the test equipment

25

and timer

12

associated with each logical group

30

of each virtual oven

10

may be physically located within the environmental stress screening room

5

. This alternative is generally not preferred because the test equipment

25

would be subjected to repeated environmental stress cycles as each logical group

30

of modules

15

is subjected to a bum-in test.

It is also possible for a virtual oven

10

to span more than one environmental stress screening room

5

. As described above, the invention divorces the conventional physical relationship of test equipment with the modules under test and replaces such conventional solutions with a logical grouping

30

of modules

15

and associated test equipment

25

. Having a virtual oven include more than one physical ESSR

5

, however, is generally not preferred because it complicates the connections and control routines as well as the logistics of physically loading and unloading the physical ESSRs

5

.

The virtual oven concept also permits logical groups

30

of modules

15

within one or more ESSRs

5

to be subjected to different environmental stresses. If two or more logical groups

30

are located within a single ESSR

5

(the generally preferred embodiment) then different environmental stresses may be applied by applying a different control regime and perhaps using additional equipment for different areas within the ESSR

5

.

For example, some logical groups

30

of modules

15

may be denser than others such that they have a greater thermal mass and greater hysteresis. To compensate for these differences, fans may be added to the ESSR

5

pointing at the logical group

30

. In this case, the modules

15

of this particular logical group

30

would preferably be physically located in the same area. By using and controlling the fans, for example, a different environmental stress could be applied to that particular logical group.

As stated above, any form of environmental stress parameter such as humidity, radiation, vibration or a combination thereof may be used to stress the modules

15

under test. The virtual oven

10

and/or the logical groups

30

may be used as a basis to apply additional or different stressors to the constituent modules of the group

30

or virtual oven

10

. For example, a vibrator or radiation source could be applied to some of the virtual oven(s)

10

or logical group(s)

30

to apply vibration and/or radiation thereto while the ESSR(s)

5

apply a thermal cycle to these and other virtual ovens

10

and logical groups

30

therein.

FIG. 3

illustrates another concept of the present invention, which is to time-share test equipment

25

between different modules

15

of the same logical group

30

. Such time-sharing of test equipment

25

is particularly advantageous when the test equipment is expensive or in short supply because it allows fewer sets of test equipment

25

to enable the system

1

. For example, if the modules

15

are optical communication modules then the test equipment

25

may include very expensive test equipment (e.g. Tektronix® ST 2400 Test Set) costing tens or even hundreds of thousands of dollars per test equipment set.

To enable such time-sharing of test equipment

25

, the virtual oven

10

includes a switch

35

interposed between the test equipment

25

and the logical group

30

of modules

15

under test. As will be further explained below in the operation section, during a first time period the switch

35

routes test signals between the test equipment

25

and the module

15

under active test. During this first time period, a second module

15

(labeled “module under passive test”) is not connected to the test equipment

25

. During a second time period, the switch

35

changes position and rotates the test cycle so that the module

15

previously under active test is now passively tested and vice versa.

Although

FIG. 3

shows a two-pole switch

35

to accommodate two modules

15

under test, it is to be understood that more than two modules can time-share the associated test equipment

25

. In addition, the invention may switch between different active tests instead of or in addition to switching between active and passive tests. In other words, the test cycle rotation may be between different types of active tests, different types of passive tests as well as various combinations of passive tests and active tests.

FIG. 4

illustrates the preferred way of connecting the components of the virtual oven

10

. In general, a network-based connection is preferred. Particularly, a bum-in network

20

serves as a backbone connecting a plurality of virtual ovens

10

and providing a pathway to the common database

40

.

As further shown in

FIG. 4

, each virtual oven

10

includes an extension of the burn-in network

20

to which are connected a PC (personal computer)

50

, a communications server

55

and a GPIB-ENET

70

. A plurality of test equipment (labeled “instr

1

, instr

2

, etc”)

25

are connected to the bum-in network

20

backbone via the GPIB-ENET

70

. A module rack

65

and connectors

55

provides a way of physically loading the modules

25

into the virtual oven

10

.

By using a network architecture such as the one shown in

FIG. 4

, each of the test instruments

25

is available to test any of the modules

15

loaded onto the module rack

65

. Specifically, the burn-in network

20

backbone, communications server

55

and GPIP-ENET

70

are controlled by, for example, PC

50

to route active test signals between the test instrument

25

and the module

15

being tested.

Similarly, passive test measurement values may be routed from the modules

15

to the PC

50

and commands may be routed from PC

50

to the module(s)

15

and/or test equipment. The passive test measurement values may be gathered by the electronics on board of each module

15

and/or by sensors external to the module

15

. These passive test measurement values vary depending upon the module

15

being tested but typically include such things as temperature, current, voltage and other parameters internal to the module

15

being tested. The AMS controller

100

associates the particular passive test measurements (or evaluation thereof) with the current module

15

under test so that the database

40

may track the performance or failure of each module

15

.

In contrast, the active test routes an active test signal to the module

15

which processes the test signal and sends a processed test signal to the PC

50

. The active test is a functional test of the module

15

and the processed test signal sent to the PC

50

is indicative of the functions performed by the module

15

.

Although the network architecture shown in

FIG. 4

utilizes particular types of connections and protocols such as GPIB, Ethernet and RS232 it is to be understood that other types of connections and protocols are contemplated herein. A relevant point is that the test equipment

25

, modules

15

, controller (e.g. PC

50

), and database

40

are disposed on a network architecture that can be controlled to route test signals, commands, and measurements as desired by the methods of the invention.

FIG. 5

shows another embodiment of the invention in which the virtual oven

10

subjects modules

15

to a burn-in test (graphically illustrated by the temperature cycle like the one shown in FIG.

2

). In this case, the modules

15

under test are multi-channel optical communications modules capable of handling a plurality of channels. For example, the modules

15

under test may be multi-channel (e.g. DWDM) transmitters, receivers, remodulators, selectors or transceivers.

As further shown in

FIG. 5

, a multi-channel signal generator

110

generates a multi-channel signal

112

, which is graphically illustrated therein. An optical splitter

120

connected to multi-channel signal generator

110

splits the multi-channel and provides the split multi-channel signal to each of the modules

15

under test (the first and second modules under test, it being understood that more than two modules

15

may be accommodated by the virtual oven

10

as explained above in relation to

FIGS. 1

a

and

1

b

).

Each of the modules

15

under test processes the multi-channel signal and sends the processed result to optical switch

135

. The optical switch

135

is also connected to AMS controller

100

that controls which of the processed multi-channel signals are sent to the BERT processor

150

. As further explained below in relation to the flowchart of

FIGS. 9

a

and

9

b,

AMS controller

100

controls optical switch

135

on a periodic basis in order to time-share the BERT processor

150

among the modules

15

under test.

Although the output from only one module

15

is analyzed at a time by BERT processor

150

, it is still quite useful to feed all of the modules

15

of the logical group

30

with a multi-channel signal. The reason is that the multi-channel signal exercises the modules

15

more completely than simply providing power to the modules. In other words, each module

15

under test is actively processing the multi-channel signal that requires powering internal components such as lasers and thereby subjects each modules to a wider-range of functional testing and stress.

The BERT processor

150

performs a conventional bit error rate test of the multi-channel signal processed by the current module

15

under test. BERT processor

150

may be implemented with a variety of standard or specially designed test equipment capable of performing a bit-error rate test. The results of then bit error rate test are fed to AMS controller

100

for analysis and/or storage in database

40

. The AMS controller

100

associates the particular bit error rate test with the current module

15

under test so that the database

40

may track the performance or failure of each module

15

.

A graphical user interface (GUI)

160

is preferably connected to the AMS controller

100

. GUI

160

allows an operator to view the test result, monitor the virtual oven

10

and control the virtual oven

10

in a manner more particularly described below. GUI

160

may be implemented with a conventional cathode ray tube, liquid crystal or other display technology. If a touch screen is utilized as illustrated in

FIG. 5

, then a separate input device is not necessary. Of course, separate input devices (not shown) such as a mouse or keyboard may be added so that an operator can interact and control the virtual oven(s)

10

.

FIG. 6

a

illustrates another implementation of the virtual oven

10

has many similarities to the system shown in FIG.

5

. As shown in

FIG. 6

a

, a single SONET/SDH test equipment

125

is utilized instead of the BERT processor

150

and multi-channel signal generator

110

of FIG.

5

. Moreover, the signals fed to the modules

15

under test are not necessarily DWDM or other multi-channel signals. Instead, any optical signal may be supplied by the SONET/SDH test equipment

125

via optical splitter

110

to conduct any desired optical test.

The optical signals processed by the modules

15

under test are supplied to the optical switch

135

. AMS controller

100

controls optical switch

135

in the same manner described above in relation to

FIG. 5

to time-share the SONET/SDH test equipment

125

between the plurality of modules

15

under test.

FIG. 6

b

illustrates another aspect of the invention. Namely, the virtual oven

10

illustrated in

FIG. 6

b

permits passive testing of the modules

15

. Passive testing includes self-monitoring by the modules in which test equipment included within (or added to) each module

15

may perform a test. For example, the passive test may be sensing the temperature of components such as a Bragg grating, laser diode, or other component. The module

15

may include temperature sensor(s), voltage sensors, or other test equipment that conducts passive testing of module

15

components.

The passive test measurements or results thereof are supplied by the modules

15

to the AMS controller

100

as indicated by the signal line connecting these elements. The AMS controller associates the test measurement and/or results with the particular module

15

being passively tested and supplies this data to the database

40

.

FIG. 6

c

is similar to

FIG. 6

b

but illustrates that the invention may be generalized to modules

15

other than optical communications modules. Specifically, a generalized test equipment

25

is used instead of the application specific BERT processor

150

of

FIG. 5

or the SONET/SDH test equipment

125

shown in

FIG. 6

b.

The generalized test equipment

25

illustrated in

FIG. 6

c

may perform any desired electrical, optical, electro-optical or other test on the modules

15

by supplying a signal thereto via signal splitter

210

. The signals processed by the modules

15

are then fed back to the test equipment

25

via switch

235

. AMS controller

100

controls switch

235

on a periodic basis in order to time-share the test equipment

25

between the plurality of modules

15

under test.

FIG. 6

d

illustrates another alternative of the invention, which is to utilize switch

245

in place of the signal splitter

210

of

FIG. 6

c

. This alternative is not preferred because it does not exercise all of the modules

15

under test to the same degree as when an active signal is fed to the module

15

. However, it is possible to use a switch

245

instead of a splitter

210

. The switch

245

is controlled by AMS controller

100

in the same fashion and, preferably, at the same timing as switch

235

so that the signals from test equipment

25

may be routed to a particular module

15

under test and so that the processed signal may be routed back to the test equipment

25

for evaluation.

Another alternative is to apply a more than one test signal to the modules

15

. For example, an active test signal may be combined with a noise signal in order to test the noise tolerance of module

15

. Furthermore, different type of active test signals may be sent simultaneously or in succession to the modules

15

under test in order to perform a variety of tests.

FIG. 6

e

illustrates an implementation for stress testing the modules

15

by adding noise to the test signal and/or degrading the test signal strength. In general, VOAs (variable optical attenuators)

80

,

86

and an optical noise source

25

may be utilized to degrade the test signal strength and add an adjustable amount of noise to the test signal. More specifically, an optical noise source

25

may inject noise into the optical test signal via coupler

82

.

The strength of this injected noise may be adjusted by the VOA

80

. The OSA (optical spectrum analyzer)

83

may be used to measure amount of noise (e.g. measure the optical signal-to-noise ratio (OSNR)) and send such measurements to the AMS controller

100

. The AMS controller

100

may then use measurements to control the OSNR by adjusting the VOA

80

. As an alternative, the OSNR may also be adjusted by using a VOA in the test signal path and adjusting the test signal strength relative to the noise signal strength.

The strength of the combined noise and test signal may also be adjusted with VOA

86

under the control of AMS controller

100

. In other words, the total signal strength of test signal plus noise may be degraded to place additional stress on the module

15

under test. For example, the module

15

may be a receiver and it is often quite useful to see how tolerant the receiver is to a weak signal or a weak and noisy signal. The AMS controller

100

can place such stress on the receiver by adjusting the VOAs

80

,

86

.

Moreover, the noise measurements may also be stored in database

40

and used, for example, to calculate a pass/fail value for the module under test

15

.

The optical noise source

25

may be constructed in various ways. A preferred construction is an ASE (amplified spontaneous emission) source. If the module

15

under test is a DWDM module the spectrum of the ASE should be flat so that a more-predictable amount of noise may be added to each channel of the DWDM signal.

The idea of noise loading in which noise is added to the test signal (e.g. such as with the configuration of

FIG. 6

e

) is particularly useful when testing modules

15

having error correcting functionality. A prime example of such error correction functionality that is widely used in the optical communications field is FEC (forward error correction) in which error correcting codes are incorporated into the signal and then used to correct errors that may be detected at the receiver. Such FEC circuits are quite capable of eliminating most communications errors.

Indeed, FEC circuits are almost too successful when it comes time to test a module incorporating FEC. The FEC will mask errors during the testing process such that the true performance of an FEC module will not be known. By noise loading the FEC modules, however, one can gauge the performance thereof more accurately and consistently. In other words, the FEC algorithm may correct for defects in other portions of the module

15

under test such that the performance under degraded signal conditions is unsatisfactory; this can be seen by providing a degraded, or noise loaded, signal during test. Also, the FEC circuitry (e.g. an ASIC is typically used) may also have defects, and these are more easily seen with a signal requiring extensive error correction. The coupling of this noise loaded condition with temperature cycling enables parallel testing of the FEC capability and other module defects, such as component infant mortalities and solder defects.

The switches (e.g.

235

,

245

) and splitters (e.g.

210

) used by the invention are commercially available and conventional elements and will, therefore, not be discussed further herein.

The AMS controller

100

may be implemented in a variety of ways including a personal computer (PC) loaded with software to be more fully described below, an ASIC (application specific integrated circuit), firmware, etc. It is generally preferred to use a PC for AMS controller

100

because of the low cost, wide-availability, and easy programmability of PCs. It is also preferred to use one PC and associated display terminal per virtual oven

10

. In this way, there can be provided one GUI

160

per virtual oven

10

that enables rapid understanding and control of each virtual oven

10

.

Likewise, the database

40

may be implemented with a variety of devices such as a conventional database program specially configured to store and organize the data generated by the invention. The memory device storing the database

40

may be local to the AMS controller

100

, but it is preferred to utilize a networked arrangement such as that shown in

FIG. 4

which permits the database

40

to be accessed by any of the individual AMS controllers

100

associated with each of the virtual ovens

10

.

FIG. 7

illustrates an alternative web-based architecture according to the invention. The WWW (World-Wide-Web)

700

is utilized as a medium to interconnect the components of the invention in a manner similar to that shown in FIG.

4

.

More specifically, the modules

15

(not shown ) are loaded onto the module racks

65

which, in turn, is connected to the WWW

700

via a communication server

55

. Likewise, a BERT processor

150

is connected to the WWW

700

via communications server

55

.

FIG. 7

further specifies and RS-232 communication protocol between the modules racks

65

and the communication server

55

but it is to be understood that a variety of other communications protocols could be used.

An Ethernet box

70

provides connectivity between the WWW

700

and SONET/SDH test equipment

125

. The temperature of the ESSR may be monitored by oven temp sensor

750

the reading of which may be forwarded to the WWW

700

via Ethernet box

70

. Again, the Ethernet protocol is merely an example of the variety of communications protocols that may be used by the invention.

To permit remote access to the virtual oven

10

, a laptop

730

and/or workstation

720

are provided. Laptop computer

720

may be connected to the WWW

700

via a MODEM

740

. Workstation

720

may be directly connected to the WWW

700

as shown.

PC

710

may also be connected to the WWW

700

as further shown in

FIG. 7

via an Ethernet connection. The PC

710

is intended to serve as the AMS controller

100

. With the configuration shown in

FIG. 7

a fully functional web-based remote control and monitoring system may be utilized to monitor and control the virtual oven

10

.

Operation of the Invention

FIG. 8

is a flowchart illustrating a method of operation according to the invention. This method is intended for a logical group

30

having only two modules

15

.

FIG. 9

illustrates the method for three (or more) modules

15

per logical group

30

. The method shown in

FIGS. 8 and 9

is executed by the AMS controller

100

(or PC

50

of FIG.

4

).

As indicated by the start icon in

FIG. 8

both modules

15

(labeled “first module” and “second module”) may begin their testing at the same time. To keep track of the time, the timer

12

associated with each logical group

30

may be utilized as illustrated in

FIGS. 1

a

and

1

b.

Following the processing path for the first module, the burn-in test begins with an active test. The flowchart reflects the preference for continuing the passive testing while the active testing is performed so that more data may be collected for each module

15

under burn-in test.

The initiate the active test, the AMS controller

100

switches the hardware (e.g. by controlling the switch

35

, optical switch

135

, switch

235

, switches

235

&

245

or by controlling the burn-in network

20

and communication server

55

) to feed the test signal to the first module in the virtual oven

10

.

During the active test, signals are fed to the first module in a manner illustrated in

FIGS. 4

,

5

,

6

a

-

6

e

or

7

; processed by the module

15

; and sent back to the test equipment (e.g. test equipment

25

, BERT processor

150

, or SONET/SDH test equipment

125

which are also called “active test equipment” herein). The signals fed to the first module are sufficient to exercise or otherwise perform an active, functional test of the first module.

The passive test may include sending a command to the module

15

to place the module

15

into a desired state. This step is optional but may be quite advantageous when the module

15

has a variety of operational states. Furthermore, some or all of the operational states may be activated by sending a different command to the module during subsequent iterations of the loop.

The first module is also monitored (passively tested) by the AMS controller

100

which records the passive test results in the database

40

. It is preferred that such passive test(s) run in parallel with any active tests in order to gather a fuller complement of test data.

The results of the active test are also stored and monitored (e.g. first module is actively tested the results of which are stored by the AMS controller in the database

40

).

The method then checks whether the active test time has been completed. This may be performed by the AMS controller

100

checking the timer

12

associated with the logical group

30

under test. If two modules

15

are being tested as in

FIG. 8

, then the test cycle may be divided into two even parts such that the first module is actively tested during the first half of the test cycle and the second module is actively tested during the second half of the test cycle.

If the active test cycle is not yet completed for the first module, then the active and/or passive test results (data) are checked or otherwise compared against pre-stored limits (e.g. tolerances). For example, if the BER rate exceeds the tolerance level, then the first module fails the active test. As another example, if one of the monitored parameters (e.g. temperature reading) is outside desired parameters, then the first module may also fail the passive test for that reason. Instead of using a pass/fail criteria, the invention may also flag or otherwise indicate that certain parameters are outside tolerances. Such criteria may be used by the AMS controller

100

to decide whether to subject that particular module

15

to retesting, reworking, or other action. The database

40

may store all such criteria.

The results of this data checking are then displayed by the AMS controller

100

on the GUI

160

. Furthermore, the GUI

160

may also display error messages which may be text, graphics or mix of text and graphics.

The active test for the first module continues until it is completed. When it has, the method then rotates the test cycle. In this case, the first module which previously underwent an active test should next be subjected to a passive test. By rotating the test cycle, the method ensures that each module

15

under test undergoes each part of the test cycle.

The method then checks whether the burn-in test has completed (e.g. both modules have been subjected to the active and passive test cycles). If so, then it is time to reload the virtual oven (VO) and create a next logical grouping

30

of modules

15

.

The right side of the flowchart in

FIG. 8

illustrates the passive test cycle. As mentioned above, the left side actually conducts both active and passive testing. Therefore, the right side is actually a subset of the steps performed by the left half. Therefore further explanation for the passive test cycle is not necessary.

FIG. 9

illustrates a burn-in test for three (or more) modules

15

(labeled first, second and third modules).

FIG. 9

is quite similar to

FIG. 8

so only the differences therebetween will be highlighted here.

The main difference is the rotation of test cycle step. When three (or more) modules

15

are being tested the full test cycle will include one active test cycle and (n−1) passive test cycles where n is equal to the number of modules

15

in the logical group

30

being tested.

FIG. 9

shows three modules so the test cycle (for the first module) is active→passive→passive→done. The other two modules would start in the middle of this sequence as appropriate.

Another difference is the active and passive test cycle times. When three modules

15

are being tested, the total burn-in time may be divided into three equal parts so that the test equipment

25

is time-shared equally between the modules

15

under test. When n modules

15

are being tested, the total burn-in time is divided in n parts.

Alternatively, the test cycle times may be unequal so that, for example, the first module is subjected to the active test for a longer time that the other two modules. The test cycle times may be adjusted by a user via the GUI

160

. Unequal test times may be advantageous for re-testing a component or for testing a troublesome component more rigorously than other, less troublesome components. Database

40

tracks each and every module

15

to enable easy identification of such troublesome components and a remedy therefor.

The test cycles may also start asynchronously. In other words, the active test cycle and the passive test cycle may start at different times. This may be particularly helpful when the test cycle durations are unequal. In this way, the testing resources may be most efficiently utilized.

FIG. 10

is an example of the displays that may be generated by the AMS controller

100

and displayed on GUI

160

. The preferred display provides a summary view of all modules currently being tested in the virtual oven. The logical groupings

30

are shown and labeled as “Racks” in the display. Each logical grouping

30

or rack includes a plurality of modules

15

under test which is indicated by the plurality of bars within each rack. A gas gauge is overlaid on each bar (representing a module

15

). As the test cycle progresses, the gas gauge increases in size.

Preferably the gas gauge overlays are color coded to indicate the test state. The color help menu shown in

FIG. 10

illustrates exemplary color codes which may include:

Test state

Color Code

Board idle

Light Blue

Slot Configured

White

Pre Test

Yellow

Under Test

Dark Blue

Test Done, No Errors