The present disclosure relates to a technical field of optical communication, and provides a method and an apparatus for determining maximum gain of Raman fiber amplifier. Wherein the method includes obtaining transmission performance parameters of a current optical fiber transmission line; respectively obtaining impact factors A.sub.1, A.sub.2, A.sub.4 according to a distance between a joint and a pump source, a fiber loss coefficient, and a fiber length included in the transmission performance parameters; calculating a joint loss value Att.sub.Aeff according to a distance between a joint and a pump source, a fiber loss coefficient, and looking up impact factor A.sub.3 according to Att.sub.Aeff; determining an actual maximum gain which may actually be achieved by the Raman fiber amplifier according to A.sub.1, A.sub.2, A.sub.3, A.sub.4. The actual maximum gain obtained in the present disclosure is the maximum gain that may be achieved over all input power ranges, and the original signal in system is kept to operate at a fixed gain, such that a gain locking effect is realized, and fluctuation of existing transmission signal power caused by signal change in transmission fiber link is avoided.

Disclosed herein are methods, devices, and system for beam forming and beam steering within ultra-wideband, wireless optical communication devices and systems. According to one embodiment, a free space optical (FSO) communication apparatus is disclosed. The FSO communication apparatus includes an array of optical sources wherein each optical source of the array of optical sources is individually controllable and each optical source configured to have a transient response time of less than 500 picoseconds (ps).

The present invention discloses an optical line terminal that includes one or more downstream signal processing means for generating a downstream signal, and converting data of the downstream signal into a serial data; a wavelength division multiplexing means for combining the serial data of different wavelengths together and then performing transmission of the combined signals; and one or more upstream signal processing means for extracting data of an upstream signal from the wavelength division multiplexing means. The terminal includes an extender including a first optical amplifier for amplifying the upstream signal, a second optical amplifier for amplifying the downstream signal, a Raman wavelength division multiplexing module for separating and combining data signal and pump light from Raman pump unit, and a Raman pump unit coupled to the Raman wavelength division multiplexing module to provide Raman amplification to the upstream and downstream signals.

An optical repeater in an MDM optical transmission system prevents a signal-to-noise ratio (SNR) from deteriorating due to a loss of a mode demultiplexer. The optical repeater in the MDM optical transmission system is configured to include at least one multimode optical amplifier, a mode demultiplexer, a mode multiplexer, and variable optical attenuators. One of the multimode optical amplifiers is disposed on the input side of the mode demultiplexer.

An optical repeater in an MDM optical transmission system prevents a signal-to-noise ratio (SNR) from deteriorating due to a loss of a mode demultiplexer. The optical repeater in the MDM optical transmission system is configured to include at least one multimode optical amplifier, a mode demultiplexer, a mode multiplexer, and variable optical attenuators. One of the multimode optical amplifiers is disposed on the input side of the mode demultiplexer.

An optical communication system includes a first optical communication device and a second optical communication device that transmit and receive an optical signal via an optical transmission line. The optical transmission line includes: a first section optical transmission line connected to the first optical communication device; and a second section optical transmission line connected to the second optical communication device and having fewer reflection points of the optical signal than the first section optical transmission line. The optical communication system includes: a light source; an incident portion that causes excitation light output from the light source to be incident to the second section optical transmission line and performs distributed Raman amplification on the optical signal; and a separating portion that separates the excitation light that is caused to be incident by the incident portion and transmitted through the second section optical transmission line in a direction of the first section optical transmission line.

An optical communication system includes a first optical communication device and a second optical communication device that transmit and receive an optical signal via an optical transmission line. The optical transmission line includes: a first section optical transmission line connected to the first optical communication device; and a second section optical transmission line connected to the second optical communication device and having fewer reflection points of the optical signal than the first section optical transmission line. The optical communication system includes: a light source; an incident portion that causes excitation light output from the light source to be incident to the second section optical transmission line and performs distributed Raman amplification on the optical signal; and a separating portion that separates the excitation light that is caused to be incident by the incident portion and transmitted through the second section optical transmission line in a direction of the first section optical transmission line.

The invention discloses a method of amplifying an optical signal, in particular a data signal, transmitted from a first location (A) to a second location (B) via a first transmission link (10a), wherein said optical signal is amplified by means of a transmitter side remote optically pumped amplifiers (ROPA) (18) comprising a gain medium (24), wherein the gain medium (24) of said transmitter side ROPA (18) is pumped by means of transmitter side pump power (20) provided from said first location (A), characterized in that at least a part of said transmitter side pump power (20) is provided by means of light supplied from said first location (A) to said transmitter side ROPA (18) via a portion of a second transmission link (10b) provided for transmitting optical signals from said second location (B) to said first location (A).

The invention discloses a method of amplifying an optical signal, in particular a data signal, transmitted from a first location (A) to a second location (B) via a first transmission link (10a), wherein said optical signal is amplified by means of a transmitter side remote optically pumped amplifiers (ROPA) (18) comprising a gain medium (24), wherein the gain medium (24) of said transmitter side ROPA (18) is pumped by means of transmitter side pump power (20) provided from said first location (A), characterized in that at least a part of said transmitter side pump power (20) is provided by means of light supplied from said first location (A) to said transmitter side ROPA (18) via a portion of a second transmission link (10b) provided for transmitting optical signals from said second location (B) to said first location (A).

An object is to respectively provide excitations light from a plurality of light sources to an odd number of fiber pairs. Optical amplifiers are disposed in three fiber pairs including two optical fibers through which optical signals are transmitted, respectively. The optical multiplexer/demultiplexer has inputs connected to light sources and three outputs. An optical multiplexer/demultiplexer has inputs connected to light sources and three outputs. In optical multiplexers/demultiplexers, one input is alternatively connected to any one of the three outputs of the optical multiplexer/demultiplexer, the other input is alternatively connected to any one of the three outputs of the optical multiplexer/demultiplexer, one output is alternatively connected to one optical fiber of any one of the three pairs, and the other output is alternatively connected to the other optical fiber of any one of the three pairs.