Systems and methods for a polarization matched resonator fiber optic gyroscope are provided. In one embodiment an RFOG comprises: a light source; a fiber optic ring resonator; a photodetector that outputs an electrical signal that varies as a function of optical intensity; and an input light polarization servo. A light beam from the servo is launched into the resonator ring in a first direction of circulation. The input polarization servo comprises a birefringence modulator that modulates a phase shift between two components of an input polarization state of the light beam at ω_m, the modulator is controlled to drive towards zero a 1^st harmonic of ω_m as measured in the electrical signal. The servo further comprises a tunable ½ waveplate that adjusts an amplitude of the two components of the input polarization state relative to each other. The tunable ½ waveplate is controlled to maximize a peak optical intensity as measured in the electrical signal.

A three-dimensional optical scanning vision system capable of producing high-resolution images in real-time includes an optical source (100) for pro­ducing a source light beam. The source light beam is directed to a beam splitter (104) which splits it into a local oscillator beam and a signal beam. The local oscillator beam is directed toward a photo­detector (106), while the signal light beam is directed toward a target (112). Light reflected from the tar­get (112) is received by the beam splitter (104) and directed toward a retroreflector (118) which returns the beam to the beam splitter (104) interface. Quarter wave plates (110,116) and the retroreflector (118) insure that the return light beam and the local oscil­lator beam are collimated and have the same polariza­tion state. Mixing the local oscillator beam and the return light beam occurs at the beam splitter (104) interface, thus providing coherent optical detection by the photodetector (106). The photodetector thus provides an output signal providing a high degree of information about the target. The system also includes scanner optics (2) to scan the signal light beam across the target. A processor (20) is also included for outputting a three-dimensional image of the target, and for controlling the scanner optics (2).

A three-dimensional optical scanning vision system capable of producing high-resolution images in real-time includes an optical source (100) for pro­ducing a source light beam. The source light beam is directed to a beam splitter (104) which splits it into a local oscillator beam and a signal beam. The local oscillator beam is directed toward a photo­detector (106), while the signal light beam is directed toward a target (112). Light reflected from the tar­get (112) is received by the beam splitter (104) and directed toward a retroreflector (118) which returns the beam to the beam splitter (104) interface. Quarter wave plates (110,116) and the retroreflector (118) insure that the return light beam and the local oscil­lator beam are collimated and have the same polariza­tion state. Mixing the local oscillator beam and the return light beam occurs at the beam splitter (104) interface, thus providing coherent optical detection by the photodetector (106). The photodetector thus provides an output signal providing a high degree of information about the target. The system also includes scanner optics (2) to scan the signal light beam across the target. A processor (20) is also included for outputting a three-dimensional image of the target, and for controlling the scanner optics (2).

The invention provides methods and devices for processing an optical signal. In one embodiment, an optical device (101) for scrambling an input optical signal comprises an optical switch (10) which switches the optical signal between two intermediate optical paths (13,14) under control of a scrambling signal from a control circuit (12). The polarisation of the signal in one of the intermediate optical paths (13) is rotated by a TE-TM converter (15). The polarisations of the two intermediate signals are thereby made mutually orthogonal. These mutually orthogonal signals are then recombined by a directional coupler (16) to provide a combined output optical signal with a scrambled polarisation alternating between othogonal states according to the frequency of the scrambling signal.

The invention may be applied to improve signal reception, for example, in coherent optical transmission systems.

An optical parametric oscillator, OPO, for generating an optical frequency comb is described. The OPO is configured to control cavity dispersion such that the OPO is able to generate extended signal and/or idler spectra in response to a continuous-wave pump. Each spectrum comprises multiple modes that are substantially equispaced with substantially the same frequency spacing.

A coherent optical mixer circuit is provided that can measure a phase error without requiring a step of cutting away a delay circuit. Odd-numbered or even-numbered two of four inputs of an 4-input-and-4-output multimode interference circuit are connected to an input mechanism. The four outputs of the multimode interference circuit are all connected to an output mechanism to the exterior. Other two inputs of the multimode interference circuit are connected to two monitor waveguides. One of the monitor waveguide is longer than the other to configure a light delay circuit. The monitor waveguides constituting the light delay circuit are connected to the respective outputs of a 2-branched light splitter. The 2-branched light splitter has an input connected to a monitor light input mechanism from the exterior via a monitor input waveguide.

According to an aspect, the present invention relates to an optical communication system for transmitting digital optical signals comprising a data generator adapted to generate a digitally encoded data signal comprising sequences of data at a data rate and comprising two signal levels representing a first state and a second state of the data signal; an optical source adapted to receive the data signal and to produce an optical signal substantially frequency modulated with frequency excursion Δν comprising a first instantaneous frequency (von) associated to the first state and a second instantaneous frequency (ν₁) associated to the second state; an optical converter that receives the substantially frequency modulated (FM) optical signal and has an optical transfer function varying with frequency and including at least one pass band with at least a peak transmittance and at least a low-transmittance region, wherein the first frequency of the FM optical signal is spectrally aligned with the low-transmittance region of the optical transfer function of the optical converter so as to convert the substantially FM signal into a substantially amplitude modulated (AM) signal and the at least one pass band has a FWHM comprised between 70% and 200% of the data rate of the FM optical signal

According to a second aspect, the present invention relates to an optical communication system including an electrical signal path between a data generator and an optical source emitting a substantially FM optical signal with frequency excursion Δν, the electrical signal path being adapted to receive the data signal generated by the data generator and to input the data signal into the optical source and having a low-pass transfer function with a cut-off frequency f_c not larger than about 2.2(Δν).

Gegenstand der Anmeldung sind ein interferometrischer Halbleiterlaser (YL) sowie optoelektronische Anordnungen mit einem solchen Laser. Der Laser besitzt ein besonderes Auskoppelsegment (Z), das es gestattet, hohe optische Leistung zu entnehmen, ohne das Filterverhalten des Lasers zu beeinflussen oder den Durchstimmbereich des Lasers wesentlich einzuschränken. Besonders verlustarm ist eine mit dem erfindungsgemäßen Laser mögliche Kopplung zu einem nachfolgenden optoelektronischen Bauelement (z.B. einem Wellenlängenkonverter (WK)) das mit dem Laser zusammen, monolithisch integriert aufgebaut wird.