An optical modulator combines and inputs a signal light propagating through the optical network and a control light having information concerning the optical network to a nonlinear optical medium. The optical modulator modulates the signal light according to changes in intensity of the control light, in the nonlinear optical medium.

An optical transmission device includes: an optical splitter configured to branch signal light input from a first optical network; a variable optical attenuator configured to control an attenuation amount of first branched signal light branched by the optical splitter and output the first branched signal light for a second optical network; and a controller configured to detect a modulation component of a signal superimposed on the signal light from second branched signal light branched by the optical splitter and control, based on the detected modulation component, an attenuation amount of the variable optical attenuator, so that the modulation component is suppressed.

An optical transmission system includes comprising: a first optical transmission apparatus to transmit wavelength-multiplexed optical signals; and a second optical transmission apparatus to receive the wavelength-multiplexed optical signals, the second optical transmission apparatus including: a receiver to perform digital coherent reception; a wavelength spacing monitor to transform a reception signal obtained by the digital coherent reception from a time domain signal to a frequency domain spectrum signal, and to monitor wavelength spacing of the spectrum signal; and a transmitter to transmit, to the first optical transmission apparatus, wavelength control information according to a monitor result obtained by the wavelength spacing monitor or the monitor result, wherein the first optical transmission apparatus includes: a receiver to receive the wavelength control information or the monitor result; and a control unit to control the wavelength spacing based on the wavelength control information or the monitor result received by the receiver.

An optical modulator combines and inputs a signal light propagating through the optical network and a control light having information concerning the optical network to a nonlinear optical medium. The optical modulator modulates the signal light according to changes in intensity of the control light, in the nonlinear optical medium.

The embodiments of the present application provide a multipath interference detection method and apparatus, and an optical module and a communication device. The method comprises: receiving a first signal; and performing detection on a frequency in the first signal, wherein if a first optical module detects, from the first signal, only a first frequency corresponding to first information, it is determined that multipath interference is not detected, and/or if the first optical module detects, from the first signal, at least a second frequency corresponding to second information, it is determined that multipath interference is detected, the first information being service information sent by a second optical module, and the second information being service information sent by the first optical module.

An optical signal processing apparatus includes a removal unit and a superimposition unit. The removal unit receives, from a first optical transmission path, an optical signal converted from an electrical signal, in which a first signal and a second signal having different frequencies from each other have been superimposed, and removes the second signal from the optical signal which has been input. The superimposition unit superimposes a third signal having a frequency different from a frequency of the first signal on the optical signal in which the second signal has been removed by the removal unit, and outputs the optical signal in which the third signal has been superimposed to a second optical transmission path.

In some embodiments, an apparatus includes a first optical transceiver. The first optical transceiver includes a set of optical transmitters, an optical multiplexer operatively coupled to the set of optical transmitters, and a variable optical attenuator operatively coupled to the optical multiplexer. The variable optical attenuator is configured to receive a control signal from a controller of the first optical transceiver and modulate a signal representing control information with an output from the optical multiplexer. The control information is associated with the control signal and for a second optical transceiver operatively coupled to the first optical transceiver.

An optical transmission device includes a transmission unit, a filter unit, a detection unit, and a control unit. The transmission unit superimposes identical superimposition signals of a frequency modulation method on a plurality of optical signals that have identical destinations and that have adjacent wavelengths, and transmits resultant signals as one communication signal. The filter unit filters part of two optical signals having adjacent wavelengths from among the plurality of optical signals included in the communication signal. The detection unit generates an electric signal of a detection level representing an optical intensity of the two optical signals that were filtered by the filter unit. The control unit controls timings of superimposing the superimposition signals on the two optical signals respectively by controlling the transmission unit so that variation in the detection level becomes smaller.

There is provided a receiving device including a receiver configured to receive a signal including at least data information and control information; a monitor configured to monitor the control information included in the signal received by the receiver; and a controller configured to control the monitor to start monitoring the control information when a strength of the signal is equal to or lower than a predetermined value.

A multifunctional laser driving circuit, and an optical module and method of using the same, are disclosed. The circuit combines first and second optical signals having different functions to form a compound signal, and switches among the first optical signal, second optical signal and compound signal by enabling or disabling first and second laser drivers corresponding to the first and second optical signals. The circuit can provide functions to optical modules, including converting an electrical data signal into an optical data signal; converting an electrical line monitoring signal into an optical line monitoring signal; combining the optical data and line monitoring signals and synchronously transmitting them to a fiber; and providing an OTDR function. Relative to using external OTDR tools to detect line faults, the present circuit and method enables simple line connection, timely detection of lines faults, and low costs of implementation.