140 results about "Homodyne detection" patented technology

An optical receiver having a plurality of optical IQ modulators arranged in a butterfly configuration and configured to operate as an optical polarization de-multiplexer. The optical receiver further has (i) an opto-electric circuit configured to apply optical homodyne detection to an optical input signal received by the optical receiver and (ii) a controller configured to generate one or more control signals for driving the IQ modulators of the plurality based on one or more electrical feedback signals received from the opto-electric circuit.

A WDM communication system having two optical-frequency comb sources (OFCSs) that are substantially phase-locked to one another, with one of these OFCSs used at a transmitter to produce a WDM communication signal and the other OFCS used at a receiver to produce multiple local-oscillator signals suitable for homodyne detection of the WDM communication signal received from the transmitter. In one embodiment, the transmitter has (i) a first OFCS adapted to generate a first frequency comb and (ii) an optical modulator adapted to use the first frequency comb to generate a WDM communication signal having at least two beacon lines for transmission to the receiver. The receiver has a second OFCS adapted to produce a second frequency comb having the beacon frequencies, with the phases of the corresponding comb lines being locked to the phases of the beacon lines of the received WDM signal.

The invention discloses a passive homodyne demodulation device and a passive homodyne demodulation method for a fai-OTDR (optical time domain reflectometer). The device consists of piezoelectric ceramics, an optical fiber coupler, a photoelectric detector, an analysis control module and a piezoelectric ceramic driver module. The method belongs to a PGC (programmed gain control)algorithm with phase modulation degree measurement improvement, the passive homodyne detection of Rayleigh scattering light phases in sensing optical fibers of the fai-OTDR is realized, the phase external modulation is carried out through PZT (plumbum-based lanthanum-doped zirconate titanate), Rayleigh scattering light and local reference light interference signals are unfolded through a Bessel function, the amplitude value of each subharmonic items unfolded by the Bessel function is analyzed, further, the phase modulation degree is obtained through analysis, and the Rayleigh scattering light phase is further solved. The structure of the device is simple, the sensitivity is high, and the performance is stable. The method has the advantages that the passive homodyne detection of the Rayleigh scattering light in the sensing optical fibers of the fai-OTDR is realized, a detecting device is simplified, and the operation cost of a system is reduced. The device and the method are applicable to optical fiber hydrophones, public security, ground invasion detection, failure positioning and the like.

The invention relates to a measuring apparatus and a measuring method. The measuring apparatus includes a light source unit configured to generate probe light, a bifurcating unit configured to cause Brillouin backscattered light occurring from the probe light to bifurcate into first light, which propagates through a first optical path, and second light, which propagates through a second optical path, a delay unit configured to delay one of the first light and the second light, an optical multiplexer configured to multiplex the first light and the second light to generate multiplexed light, and a coherent detector configured to perform homodyne detection of the multiplexed light and to output a difference frequency obtained as a result of the detection as a phase-difference signal. According to provided method, when Brillouin backscattered light is used to measure distortion of optical fibers, the measured frequency change of light is taken as the phase-difference of beat signal provided by coherent detection, and thus two-dimensional information of time and phase can be obtained.