A common component assembly is provided for a cable joint for joining a first submarine optical cable and a second submarine optical cable. The assembly includes a first end face including a first opening and a first flange for connection to a first cable termination unit of an undersea optical cable joint. The assembly also includes a second end face including a second opening and a second flange for connection to a second cable termination unit of an undersea optical cable joint. The assembly further includes a fiber tray connecting the first end face to the second end face. In addition, the assembly includes an optical assembly connected to a first side of the fiber tray. The optical assembly includes a free space optical add/drop multiplexer.

An optical add-drop device includes optical circuits. Each of the optical circuits includes first to third sub optical circuits. Each sub optical circuit includes an input coupler, output coupler, and a phase shifter. In each of the optical circuit, two ports of the output coupler in the first sub optical circuit are respectively coupled to the input coupler in the second sub optical circuit and the input coupler in the third sub optical circuit. The output coupler in the second sub optical circuit in each of the optical circuits is coupled to a drop port or the input coupler in the first sub optical circuit in the adjacent optical circuit. The input coupler in the third sub optical circuit in each of the optical circuits is coupled to an add port or the output coupler in the third sub optical circuit in the adjacent optical circuit.

Coherent optical multiplexing 1+1 protection disclosed herein uses multiplexers, each having multiplexing and demultiplexing sub-units. Relay ports of a node are connected with the multiplexers, and each relay port is configured to input and output optical signals with the corresponding multiplexer. Two transmission ports of the node are connected with disjoint paths and are configured to input and output optical signals therewith. The node includes: a first optical splitter having input ports connected with the relay ports and two output ports connected with the two transmission ports; an optical switch connected with the transmission ports respectively via two input interfaces; a second optical splitter, which is a 1N optical splitter, having one input port connected with an output interface of the optical switch and having output ports connected with the relay ports. The solution is reliable in implementation, has low insertion loss, and has good transmission performance.

Systems and methods are provided for reducing interference when optical signals are added. One embodiment includes a method for adding an optical channel for communicating data and having a bandwidth within an optical spectrum for transmission along an optical link of an optical network. The method includes creating a lower frequency holding zone having a lower frequency bandwidth adjacent to the bandwidth of the added optical channel and including at least one lower frequency sub-slice having a power spectral density that varies throughout the lower frequency sub-slice. Also, the method includes creating a higher frequency holding zone having a higher frequency bandwidth adjacent to the bandwidth of the added optical channel and including at least one higher frequency sub-slice having a power spectral density that varies throughout the higher frequency sub-slice. The lower frequency holding zone and the higher frequency holding zone are dynamically configured with respect to fiber and channel requirements.

A de-multiplexer (1) for separating two co-propagating modes of electromagnetic radiation includes a volume (2) having a path therethrough for receiving electromagnetic radiation, an input (8) for directing two co-propagating modes of electromagnetic radiation to be incident upon the volume, a control source (12) of electromagnetic radiation arranged to generate a time-dependent control field. The volume is arranged and the time-dependent control field is shaped such that, when the two co-propagating modes of electromagnetic radiation and the time-dependent control field are incident upon the volume contemporaneously, the time-dependent control field causes the volume to accept one of the two modes of electromagnetic radiation onto a mode of the volume without any parametric non-linear optical interaction taking place and to reflect or transmit the other of the two modes of electromagnetic radiation, so to spatially and/or temporally separate the two modes of electromagnetic radiation from each other.

A frequency stabilizer includes: a delay line interferometer that receives an optical signal corresponding to one frequency mode of a pulsed laser, divides and transmits the received optical signal to a reference arm and a delay arm including an optical fiber delay line, and then outputs an interference signal between signals passing through the reference arm and the delay arm; a photoelectric converter that converts the interference signal into an electrical signal; a mixer that generates a baseband signal of the electrical signal by mixing a carrier frequency signal; and a feedback controller that transmits a control signal generated based on the baseband signal to the pulsed laser. The optical signal passing through the delay arm is weighted with a delay time caused by the optical fiber delay line compared to the optical signal passing through the reference arm, and the optical signal passing through the delay arm is frequency shifted to a carrier frequency of an oscillator. A carrier-envelope offset frequency of the pulsed laser is stabilized by an offset frequency stabilizer.

An optomechanical device for modulating an optical signal for reducing thermal noise and tracking mechanical resonance of a proof mass assembly comprises a circuit configured to receive, from a light-emitting device, the optical signal and modulate the optical signal to remove thermal noise and to drive a mechanical response frequency to the mechanical resonance of the proof mass assembly using a cooling feedback signal and a mechanical resonance feedback signal. The circuit is further configured to generate, using the modulated optical signal, the cooling feedback signal to correspond to a thermal noise signal of the modulated optical signal with a total loop gain of zero and a phase difference of 180 degrees and generate, using the modulated optical signal, the mechanical resonance feedback signal to drive the mechanical response frequency of the modulated optical signal to the mechanical resonance.

An optical fiber transmission system and method for using the system are provided. The system may include a span of transmission fiber for transmitting light signals through the optical fiber transmission system. The system may include a dispersion compensating module coupled to the span of transmission fiber. The system may include a switchable module including a set of selectable light signal paths, the set of selectable light signal paths including at least one path through a dispersion compensating element. The system may include a processor coupled to the switchable module for selectively monitoring the set of selectable light signal paths, where the processor is further configured to derive a metric based on the set of selectable light signal paths for controlling the dispersion compensating module.

An optomechanical device comprising a circuit configured to generate an optical signal using a tuning signal and modulate the optical signal at a frequency corresponding to one quarter of a Full Width at Half Maximum (FWHM) of an optical resonance of the proof mass assembly to generate a partially modulated optical signal. The circuit being further configured to filter the partially modulated optical signal to remove a central carrier from the partially modulated optical signal to generate a filtered optical signal, modulate the filtered optical signal to generate a modulated optical signal driven to the mechanical resonance of the proof mass assembly, and generate the tuning signal using a difference between a DC intensity level of a first optical frequency component in the modulated optical signal and a DC intensity level of a second optical frequency component in the modulated optical signal.

Systems and methods for controlling optical powers of optical channels in an optical communications network comprising a plurality of nodes is described herein. The method comprises obtaining a reference optical power. The method also includes determining an optical power of an optical channel generated by an optical transmitter of a node. The method further includes applying an attenuation to the optical channel to reduce the optical power of the optical channel to the reference optical power. In some implementations, the method is performed by a network controller operating in the optical communications network.