An optical reception apparatus (1) of the present invention includes: a local oscillator (11) outputting local oscillation light (22); an optical mixer (12) receiving a multiplexed optical signal (21) and the local oscillation light, and selectively outputting an optical signal (23) corresponding to the wavelength of the local oscillation light from the multiplexed optical signal; a photoelectric converter (13) converting the optical signal (23) output from the optical mixer into an electric signal (24); a variable gain amplifier (15) amplifying the electric signal (24) to generate an output signal (25) whose output amplitude is amplified to a certain level; a gain control signal generating circuit (16) generating a gain control signal (26) for controlling the gain of the variable gain amplifier (15); and a monitor signal generating unit (17) generating a monitor signal (27) corresponding to the power of the optical signal (23) using the gain control signal (26).

An optical reception apparatus (1) of the present invention includes: a local oscillator (11) outputting local oscillation light (22); an optical mixer (12) receiving a multiplexed optical signal (21) and the local oscillation light, and selectively outputting an optical signal (23) corresponding to the wavelength of the local oscillation light from the multiplexed optical signal; a photoelectric converter (13) converting the optical signal (23) output from the optical mixer into an electric signal (24); a variable gain amplifier (15) amplifying the electric signal (24) to generate an output signal (25) whose output amplitude is amplified to a certain level; a gain control signal generating circuit (16) generating a gain control signal (26) for controlling the gain of the variable gain amplifier (15); and a monitor signal generating unit (17) generating a monitor signal (27) corresponding to the power of the optical signal (23) using the gain control signal (26).

An injection locked transmitter for an optical communication network includes a primary seed laser source input substantially confined to a single longitudinal mode, an input data stream, and a laser injected modulator including at least one secondary laser having a resonator frequency that is injection locked to a frequency of the single longitudinal mode of the primary seed laser source. The laser injected modulator is configured to receive the primary seed laser source input and the input data stream, and output a laser modulated data stream.

An injection locked transmitter for an optical communication network includes a primary seed laser source input substantially confined to a single longitudinal mode, an input data stream, and a laser injected modulator including at least one secondary laser having a resonator frequency that is injection locked to a frequency of the single longitudinal mode of the primary seed laser source. The laser injected modulator is configured to receive the primary seed laser source input and the input data stream, and output a laser modulated data stream.

[Problem] An optical receiver using a polarization demultiplexing technique is miniaturized. [Solution] An optical receiver 100A for receiving a polarization multiplexed signal obtained by performing orthogonal polarization multiplexing on two optical signals. The optical receiver includes an IL 1 splitting the polarization multiplexed signal into two transmitted signals that are asymmetric in terms of a light transmission characteristic, O/Es 2a and 2b converting the transmitted signals resulting from the split into electrical signals, a downsampler 3 downsampling the electrical signals resulting from the conversion to generate low-speed digital signals, a calculator 4 calculating coefficients of a polarization separation matrix from the resultant low-speed digital signals, a level adjuster 5A adjusting, in accordance with the coefficients resulting from the calculation, signal levels of the electrical signals resulting from the conversion to generate a plurality of adjustment signals, adders 6Aa and 6Ab adding the generated adjustment signals to generate addition signals, and discriminators 7a and 7b restoring and extracting the two optical signals from the generated addition signals.

[Problem] An optical receiver using a polarization demultiplexing technique is miniaturized. [Solution] An optical receiver 100A for receiving a polarization multiplexed signal obtained by performing orthogonal polarization multiplexing on two optical signals. The optical receiver includes an IL 1 splitting the polarization multiplexed signal into two transmitted signals that are asymmetric in terms of a light transmission characteristic, O/Es 2a and 2b converting the transmitted signals resulting from the split into electrical signals, a downsampler 3 downsampling the electrical signals resulting from the conversion to generate low-speed digital signals, a calculator 4 calculating coefficients of a polarization separation matrix from the resultant low-speed digital signals, a level adjuster 5A adjusting, in accordance with the coefficients resulting from the calculation, signal levels of the electrical signals resulting from the conversion to generate a plurality of adjustment signals, adders 6Aa and 6Ab adding the generated adjustment signals to generate addition signals, and discriminators 7a and 7b restoring and extracting the two optical signals from the generated addition signals.

Coherent optical communications technology for recovery of 1D and 2D formatted optical signals. For example, 1D or 2D formatted signals that travel through fiber optic media may be recovered by separating the light into X- and Y-polarization components, rotating one polarization component (e.g., Y-component) into the polarization space of the other component (e.g., Y-component into the X-polarization space), delaying the rotated component enough to avoid destructive interference and combining the delayed component with the undelayed component to form a folded optical signal, which may then be processed as a X-polarized signal.

An optical apparatus includes a front optics section and a spectrometer section. The front optics section includes a spot de-multiplexer configured to receive a plurality of multi-mode optical signals each having a plurality of modal components, and to output in a linear array of a corresponding plurality of optical beams for each multimode optical signal. The spectrometer section includes a wavelength steering element configured to separate each of the optical beams into a plurality of wavelength channels. A fiber steering element is configured to steer the wavelength channels between the optical beams.

An optical apparatus includes a front optics section and a spectrometer section. The front optics section includes a spot de-multiplexer configured to receive a plurality of multi-mode optical signals each having a plurality of modal components, and to output in a linear array of a corresponding plurality of optical beams for each multimode optical signal. The spectrometer section includes a wavelength steering element configured to separate each of the optical beams into a plurality of wavelength channels. A fiber steering element is configured to steer the wavelength channels between the optical beams.

A system and method including polarization modulation of supervisory signals for reducing interference with data signals in a wavelength division multiplexed optical communication system. At least one supervisory signal for monitoring a transmission path and/or elements coupled to the transmission path is fast polarization modulated and launched with data signals onto the path. Polarization modulating of the supervisory signal reduces impact of the supervisory signal on the data signals and improves system performance.