Consistent with the present disclosure, a photonic integrated circuit (PIC) is provided that has 2 N channels (N being an integer). The PIC is optically coupled to N optical fibers, such that each of N polarization multiplexed optical signals are transmitted over a respective one of the N optical fibers. In another example, each of the N optical fibers supply a respective one of N polarization multiplexed optical signals to the PIC for coherent detection and processing. A multiplexer and demultiplexer may be omitted from the PIC, such that the optical signals are not combined on the PIC. As a result, the transmitted and received optical signals incur less loss and amplified spontaneous emission (ASE) noise. In addition, optical taps may be more readily employed on the PIC to measure outputs of the lasers, such as widely tunable lasers (WTLs), without crossing waveguides

Example embodiments of the present invention relate to programmable ROADMs used to construct optical nodes. Example embodiments include wavelength switches and waveguide switches, wherein the waveguide switches may be programmed to direct wavelength division multiplexed optical signals to and from the wavelength switches.

A method of loading a fiber optic transport system includes detecting optical power in a frequency sub-band of optical spectrum, wherein the frequency sub-band includes data-bearing channels and at least one control channel; measuring optical power in the frequency sub-band; and adjusting optical power of the at least one control channel based on the measured optical power, wherein the optical power is adjusted through one of changing a current of control channel lasers and controlling a set of fast optical attenuators.

A reconfigurable optical add/drop multiplexer (ROADM) includes a plurality of interconnected ROADM blocks. Each ROADM block includes an ingress switchable-gain amplifier, an output power detector coupled to an output of the ingress switchable gain amplifier, and a wavelength-selective switch coupled to the output of the ingress switchable gain amplifier. Each ROADM block includes a plurality of add/drop blocks coupled to the wavelength-selective switches of the plurality of ROADM blocks. The ROADM includes a controller configured to receive an indication of an output signal power from the output power detector and adjust gain and equalization parameters of the ingress switchable-gain amplifier based on the received indication of the output signal power.

In order to provide a feature with which it is possible to suppress the occurrence of an optical surge independently of the type of optical switch, there is provided an optical control device for processing inputted first light and outputting second light, wherein the optical control device is provided with: a switching unit for switching and outputting first light that has undergone a selected process; and a variable output unit connected in series to the switching unit, the variable output unit operating so as to reduce the optical power of the second light before switching by the switching unit is executed and to gradually increase the optical power of the second light after the switching is executed.

A multiplexer inserts a dummy signal light into a main signal. A light intensity monitor acquires the intensity of the light of each wavelength of a light output from a wavelength selective switch. A light source controller controls the insertion of the dummy signal light into the main signal, and release of the insertion. A difference calculator calculates the difference between a first light intensity that has been acquired in a state in which the dummy signal light is inserted into the main signal and a second light intensity that has been acquired in a state in which the dummy signal light is not inserted into the main signal. An insertion loss calculator calculates an insertion loss in the wavelength selective switch based on the calculated difference. An insertion loss controller controls the insertion loss in the wavelength selective switch based on the calculated insertion loss.

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 communication system includes a plurality of optical system nodes, a plurality of optical space switches and a plurality of optical fibers. The plurality of optical system nodes each includes at least one reconfigurable optical add/drop multiplexer (ROADM). The optical system nodes each have at least one client side port and at least one line side port. Each optical space switch is operatively coupled to the line side port of one of the plurality of optical system nodes. Each of the optical fibers couples one of the optical space switches to another of the optical space switches.

A method of loading a fiber optic transport system includes adding one or more control channels to an optical fiber having one or more channels, wherein each of the control channels comprises a pair of signals that are cross-polarized and each of the pair of signals is at a different frequency from one another; measuring optical power on the optical fiber; and adjusting optical power of the one or more control channels based on the measured optical power.

An optical signal monitor, including: a storage that holds a threshold value set for each of determination areas having a bandwidth set in accordance with an average grid of dummy light; a measurement section that sequentially measures an optical intensity of an inputted wavelength-multiplexed optical signal with respect to each of measurement areas obtained by dividing the determination area into areas with a bandwidth sufficiently smaller than a grid width of a monitoring-target optical signal composing the wavelength-multiplexed optical signal, and output measured values; and a section that determines that dummy light corresponding to the determination area needs introducing if each of measured values in the determination area is smaller than a threshold value, and, determines that dummy light corresponding to the determination area does not need introducing if at least one of the measured values in the determination area is equal to or larger than the threshold value.