An optical amplifier repeater system includes an optical fiber propagating a light beam in a plurality of propagation modes and an optical amplifier repeater amplifying the light beam propagated through the optical fiber. The optical amplifier repeater includes an optical demultiplexer demultiplexing the light beam in the plurality of propagation modes propagated through the optical fiber into a plurality of single-mode light beams, an optical amplifier amplifying, by simultaneous pumping, intensities of the plurality of single-mode light beams using a light beam generated by one pumping light source, an optical multiplexer multiplexing the plurality of single-mode light beams amplified by the optical amplifier into a light beam in the plurality of propagation modes, and an optical intensity adjusting unit adjusting the intensity of each of the plurality of single-mode light beams at least one of before or after the amplification by the optical amplifier. The optical intensity adjusting unit performs the adjustment by amplifying or attenuating the optical intensity of each of the plurality of single-mode light beams in an individual optical path through which the single-mode light beam is propagated.

A communication system that includes a first optical node at a first location in a defined indoor area and a second optical node at a second location, where each of the first optical node and the second optical node comprises one or more first type of sensors. The first optical node establishes RF supervisory link with second optical node and performs a first optical alignment with the second optical node based on sensor measurements from the one or more first type of sensors. The sensor measurements are exchanged between the first optical node and the second optical node over the established RF supervisory link for the first optical alignment. The first optical node performs a second optical alignment with the second optical node and establishes a free-space optical link as a laser backhaul with the second optical node based on the first optical alignment and the second optical alignment.

Disclosed herein are methods and systems for optimizing signal quality in an optical network having two or more hub nodes continuously outputting optical signals to a plurality of leaf nodes. Each of the plurality of leaf nodes may receive a combined optical signal from the hub nodes and determine an optical power and a signal quality of one optical subcarrier group and send a correction signal to the hub node that sent the subcarrier group. The hub nodes may send a power optimization request comprising the optical power and signal quality of each subcarrier group to a network controller. The network controller may use the optical power and signal quality to determine a power update for an optical power of the subcarrier group(s) and send the power update to the hub node transmitting the subcarrier group. The hub node may adjust the optical power based on the power update.

A method of controlling an optical amplifying system that processes an optical signal with the PAM4 mode is disclosed. The optical amplifying system includes variable optical attenuator (VOA) and a semiconductor optical amplifier (SOA). The VOA attenuates the optical signal such that maximum optical power thereof corresponding to one of the physical levels of the PAM4 signal becomes equal to a preset optical level for which the SOA may linearly operable. The SOA may amplify thus attenuated optical signal with a fixed optical gain.

An optical transmission device includes: a memory; and a processor coupled to the memory; the processor: generate a first symbol by mapping a transmission data series to a first signal point which belongs to a first group within a signal space defined with regard to characteristics of an optical carrier wave of the transmission data series; generate a second symbol by mapping the transmission data series to a second signal point belonging to a second group; calculate a perturbation quantity of a signal electric field for each of the first and second symbols based on signal electric field vector information of a symbol which is generated before the first symbol and the second symbol; and determine, as a transmission signal, a symbol having a smaller perturbation quantity between the first symbol and the second symbol.

Methods and systems are disclosed for characterizing a polarization-dependent loss or gain (PDL/G) of an optical device under test (DUT), such as an optical fiber link, from an optical signal having passed through the optical DUT. The optical signal is substantially unpolarized upon entering the optical DUT. The method can include varying a state of polarization (SOP) of the optical signal over a plurality of sampled SOP conditions to produce a respective plurality of SOP-varied optical signals; performing a polarization-analysis and detection operation on the plurality of SOP-varied optical signals to acquire a respective plurality of detected signal sets, each detected signal set including at least one polarization-analyzed detected signal; and determining, as the PDL/G of the optical DUT, a polarization extinction ratio parameter representative of a ratio of maximum to minimum power levels measured among the polarization-analyzed detected signals of the plurality of detected signal sets.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.

According to one embodiment, a communication repeater system includes a master station device and radio frequency units which convert a signal from each of base station systems into an optical digital signal for transmission to the master station device. The base station systems establish communication by time division duplex scheme. The communication repeater system repeats communication between a mobile communication terminal device and each base station system via a corresponding one of slave station devices. A setter sets, as reference transmission/reception switching timing, a transmission/reception switching timing between the master station device and one of the radio frequency units corresponding to one of the base station systems which is first connected to the communication repeater system. A corrector corrects variation in the transmission/reception switching timing in accordance with the reference transmission/reception switching timing.

According to one embodiment, a communication repeater system includes a master station device and radio frequency units which convert a signal from each of base station systems into an optical digital signal for transmission to the master station device. The base station systems establish communication by time division duplex scheme. The communication repeater system repeats communication between a mobile communication terminal device and each base station system via a corresponding one of slave station devices. A setter sets, as reference transmission/reception switching timing, a transmission/reception switching timing between the master station device and one of the radio frequency units corresponding to one of the base station systems which is first connected to the communication repeater system. A corrector corrects variation in the transmission/reception switching timing in accordance with the reference transmission/reception switching timing.

A configuration for receiving transmission data at multiple rates where one rate is not necessarily a multiple of another is provided. A host board includes a receiving circuit, a cross point switch, and a switch control circuit. The receiving circuit includes a receiving unit configured to receive a first data signal transmitted at a first rate, and a second receiving unit configured to receive a second data signal transmitted at a second rate different from the first rate. The cross point switch includes input terminals and output terminals. The cross point switch is configured to define a path of signal between the input terminals and the output terminals to route an input data signal to at least one of the first receiving unit and the second receiving unit.