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.

A receiving device receives a received signal in which a data signal, modulated by using a phase modulation method, and a pilot signal are time-multiplexed. The receiving device includes a synchronizing circuit that synchronizes the phase of the received signal. The synchronizing circuit extracts a pilot signal from the received signal. The synchronizing circuit estimates a phase error by comparing the extracted pilot signal and a predetermined pattern. The synchronizing circuit conducts phase rotation on constellation points of the received signal in accordance with the reference phase, obtained from the phase error, and the phase in the modulation method related to the received signal. The synchronizing circuit estimates a phase estimate value of the received signal in accordance with the constellation points, on which phase rotation has been conducted. The synchronizing circuit compensates for a phase error of the received signal in accordance with the phase estimate value.

In a method in which a compensation coefficient calculating portion (6) calculates a compensation coefficient of a compensation portion (5) which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.

An optical network element for a hardware configured optical network includes a first optical port that receives an input optical signal comprising receive control information from the hardware configured optical network. A demodulator optically coupled to the first optical port decodes the receive control information for configuring the optical network element. A modulator having an electrical modulation input that receives transmit control information imparts a modulation onto an optical carrier thereby generating a transmit optical control signal representing the transmit control information. A second optical port transmits the transmit optical control signal representing the transmit control information to the hardware configured optical network.

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 present disclosure provides an optical module comprising: a photoelectric conversion unit, a first demodulation circuit, and a second demodulation circuit; the first demodulation circuit and the second demodulation circuit are respectively connected to the photoelectric conversion unit; the photoelectric conversion unit is configured to convert the received optical signal into an electrical signal; the first demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a high-frequency electrical signal; the second demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a low-frequency electrical signal.

A downhole tool apparatus is disclosed that includes an input fiber optic cable coupled to an electro-optic modulator. The input fiber optic cable propagates first and second actively orthogonally polarized light beams. The electro-optic modulator modulates the first and second actively orthogonally polarized light beams in response to a measurement data stream (e.g., telemetry data). A single light beam comprising the modulated first and second actively orthogonally polarized light beams is propagated over an output fiber optic cable so that the modulated first and the second actively orthogonally polarized light beams propagate the same data through the output fiber optic cable. Recovery circuitry coupled to the single light beam is then used to detect, demodulate, and decode the original measurement data stream.

A method for configuring hardware-configured optical links includes generating a first optical signal comprising a slow scan of wavelength channels where the slow scan has a dwell time on a particular wavelength channel. A second optical signal is generated comprising a fast scan of wavelength channels, where the fast scan has a dwell time on a particular wavelength channel and a complete channel scan time where the slow scan dwell time is greater than or equal to complete channel scan time. The first optical signal is transmitted over a link and a portion is then detected. A pulse of light having a duration that is less than the dwell time on the particular wavelength channel of the fast scan is then detected. Client data traffic is then sent over the link in response to the detected pulse of light and the detected portion of the first optical signal.

In a method in which a compensation coefficient calculating portion (6) calculates a compensation coefficient of a compensation portion (5) which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.

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.