An object is to be capable of housing an optical fiber that connects between components not to exceed a bending limit of the optical fiber in a housing of a pluggable optical module. A pluggable electric connector (11) is configured to be insertable into and removable from an optical communication apparatus (93). An optical output module (12) outputs an optical signal (LS1) and a local oscillation light (LO). An optical reception module (13) outputs a communication data signal (DAT) generated by demodulating using the local oscillation light (LO). A pluggable optical receptor (15) is configured in such a manner that optical fibers are insertable thereinto and removable therefrom. A first optical fiber (F11) is connected between the optical output module (12) and the pluggable optical receptor (15). A second optical fiber (F12) is connected between the optical output module (12) and the optical reception module (13). A third optical fiber (F13) is connected between the optical reception module (13) and the pluggable optical receptor (15). Optical fiber housing means winds extra lengths of the first to third optical fibers (F11 to F13) around a guide.

An optical frequency comb device includes: an optical waveguide; a first mirror disposed at a first position in the optical waveguide; a second mirror disposed at a second position different from the first position, in the optical waveguide; a gain medium and a saturable absorber which are disposed between the first mirror and the second mirror; and a controller that fixes one of a repetition frequency and a carrier-envelope offset frequency of an optical frequency comb output from an end of the optical waveguide, and changes the other of the repetition frequency and the carrier-envelope offset frequency.

An optical frequency comb device includes: an optical waveguide; a first mirror disposed at a first position in the optical waveguide; a second mirror disposed at a second position different from the first position, in the optical waveguide; a gain medium and a saturable absorber which are disposed between the first mirror and the second mirror; and a controller that fixes one of a repetition frequency and a carrier-envelope offset frequency of an optical frequency comb output from an end of the optical waveguide, and changes the other of the repetition frequency and the carrier-envelope offset frequency.

The present invention provides an optical phase synchronization method characterized by involving applying a small phase modulation signal (dither signal) to local oscillator light, acquiring an error signal that is dependent on a phase shift, and controlling the phase shift. The present invention further provides an optical phase synchronization method characterized by involving inducing a specific phase pattern in dummy pulses in an optical resonator using injection light, applying phase modulation to the local oscillator light, and thereby acquiring a part of the measurement result of the dummy pulses as the error signal. The present invention is further characterized by arranging calculation pulses and phase synchronization dummy pulses in a distributed manner (for example, alternately) and increasing a pulse width using a narrow band electrical filter.

The present invention provides an optical phase synchronization method characterized by involving applying a small phase modulation signal (dither signal) to local oscillator light, acquiring an error signal that is dependent on a phase shift, and controlling the phase shift. The present invention further provides an optical phase synchronization method characterized by involving inducing a specific phase pattern in dummy pulses in an optical resonator using injection light, applying phase modulation to the local oscillator light, and thereby acquiring a part of the measurement result of the dummy pulses as the error signal. The present invention is further characterized by arranging calculation pulses and phase synchronization dummy pulses in a distributed manner (for example, alternately) and increasing a pulse width using a narrow band electrical filter.

Devices, systems and methods for encoding information using optical components are described. An example photonic filtered sampler includes a spectral shaper configured to receive an optical pulse train, a dispersive element positioned to receive an output of the spectral shaper and to expand spectral contents thereof in time, and a modulator configured to receive an output of the dispersive element and a radio frequency (RF) signal, and to produce a modulated output optical signal in accordance with the RF signal. In this configuration, one or more characteristics of the modulated output optical signal is determined based on a spectral shape provided by the spectral shaper and dispersive properties of the dispersive element.

A wavelength conversion device includes a second-order nonlinear optical medium with a polarization inversion structure, wherein the wavelength conversion device performs wavelength conversion between three wavelengths according to a relationship of 1/λ.sub.1=1/λ.sub.2+1/λ.sub.3, a polarization inversion period Λ of the polarization inversion structure is divided into 2a regions, and when the 2a regions divided from the polarization inversion period Λ each has a width ratio of an inverted region and a non-inverted region of r to 1−r (where 0≤r≤1), a ratio value r is set such that, when one period in phase of a sine function from 0 to 2π is divided into 2a regions, a value of the sine function in a center of each divided region is (1−2r)±0.1.

An optical microphone includes: a light source; a first optical divider dividing light from the light source into reference light and measurement light; a second optical divider dividing the measurement light into N measurement light beams; a first emitter emitting the N measurement light beams from different positions toward a predetermined space; a first light receiver receiving the N measurement light beams having propagated through the space; a third optical divider dividing the reference light into N reference light beams; N optical couplers coupling the N measurement light beams with the N reference light beams on a one-to-one basis; N optical detectors receiving N coupled light beams and each detecting interference between the measurement light beam and the reference light beam in the corresponding coupled light beam; and a controller controlling directionality of sound pickup by performing signal processing on N detection signals from the N optical detectors.

An optical microphone includes: a light source; a first optical divider dividing light from the light source into reference light and measurement light; a second optical divider dividing the measurement light into N measurement light beams; a first emitter emitting the N measurement light beams from different positions toward a predetermined space; a first light receiver receiving the N measurement light beams having propagated through the space; a third optical divider dividing the reference light into N reference light beams; N optical couplers coupling the N measurement light beams with the N reference light beams on a one-to-one basis; N optical detectors receiving N coupled light beams and each detecting interference between the measurement light beam and the reference light beam in the corresponding coupled light beam; and a controller controlling directionality of sound pickup by performing signal processing on N detection signals from the N optical detectors.

An apparatus and method for wavelength conversion of a signal, for example, a dual-polarization signal, is disclosed. The apparatus implements a single-loop counter-propagating wavelength conversion scheme which provides both up-conversion and down-conversion of the signal within the same loop. Nonlinear wavelength conversion devices in the loop provide both up-conversion and down-conversion of the polarization components of the signal within the loop depending on whether the polarization component travels through the nonlinear conversion device in a clockwise or a counter-clockwise direction. The wavelength-converted signal is available to be extracted from the wavelength-conversion loop. An all-optical wavelength-division multiplexing transponder based on the wavelength-conversion scheme is also disclosed.