This application provides a submarine network device and a submarine cable system that may accurately detect a fault of a submarine optical repeater in time. The device comprises: a first fiber and a second fiber; at least one first pump laser, configured to supply pumping light to a first optical amplification unit located in the first fiber; the first optical amplification unit, configured to amplify and then output a first probe signal sent from a first site to a second site; a first fiber coupler located in the first fiber, configured to receive a first reflected optical signal obtained from the first probe signal after Rayleigh backscattering, and send a portion of the first reflected optical signal to a second fiber coupler located in the second fiber; at least one second pump laser, configured to supply pumping light to a second optical amplification unit; a second optical amplification unit, configured to amplify and then output a second data optical signal sent by the second site to the first site; and a second fiber coupler, configured to receive a portion of the first reflected optical signal output by the first fiber coupler.

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 subject technology relates to an in-line amplifier assembly for distributed sensing system. The subject technology includes deploying a distributed sensing tool into a wellbore, and logging the wellbore using the distributed sensing tool. The distributed sensing tool includes a first optical amplifier and a first optical filter coupled to a first single-mode optical fiber. The first optical amplifier is coupled to a first single-mode circulator for amplifying a single-mode optical signal, and the first optical filter is coupled to the first optical amplifier for filtering the amplified single-mode optical signal. The first single-mode circulator is coupleable to an interrogator for routing the single-mode optical signal to a second single-mode optical fiber and routing a reflective optical signal from a second single-mode optical fiber to the interrogator. The reflective optical signal may traverse a second optical amplifier and a second optical fiber between the first and second single-mode circulators.

A bidirectional optical transmission system includes a first optical transmission line including a first repeater (30A), a second optical transmission line including a second repeater (30B), and C+L band transmitting/receiving devices (10, 20) connected to each other through these transmission lines so that they can communicate with each other. The C+L band transmitting/receiving device (10) transmits an optical signal in a C-band to the first optical transmission line and transmits an optical signal in an L-band to the second optical transmission line, and the C+L band transmitting/receiving device (20) transmits an optical signal in the C-band to the second optical transmission line and transmits an optical signal in the L-band to the first optical transmission line. The first repeater (30A) separates the optical signal in the C-band and the optical signal in the L-band bidirectionally propagating through the first optical transmission line from each other, and separately amplifies the separated optical signals, and the second repeater (30B) separates the optical signal in the C-band and the optical signal in the L-band bidirectionally propagating through the second optical transmission line from each other, and separately amplifies the separated optical signals. In this way, it is possible to expand a transmission capacity and alleviate deterioration in a transmission characteristic.

A repeater includes a pump light supplier configured to generate pump light; a first multiplexer configured to multiplex the pump light and a first wavelength division multiplexed optical signal; a second multiplexer configured to multiplex the pump light and a second wavelength division multiplexed optical signal; a first amplifier configured to amplify the first wavelength division multiplexed optical signal by use of the pump light; a second amplifier configured to amplify the second wavelength division multiplexed optical signal by use of the pump light; and a controller configured to control power of the pump light output to the first multiplexer and the second multiplexer, based on wavelength information about at least one of the first wavelength division multiplexed optical signal and the second wavelength division multiplexed optical signal.

Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.

Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.

An excitation light source apparatus capable of assuring an excellent optical transmission characteristic even at occurrence of a gain tilt is provided. The excitation light source apparatus comprises an excitation light outputting means, a control signal detection means, a control signal detection means, an excitation light control means, and a multiplexing means. The excitation light outputting means outputs excitation light for Raman amplification. The control signal detection means detects a control signal of the excitation light outputting means from beams of WDM signal light transmitted through optical fibers in an upstream direction and a downstream direction. The excitation light control means controls the excitation light outputting means, based on the control signal. The multiplexing means multiplexes the excitation light and each of the beams of the WDM signal light, and outputs the respective multiplexed beams of light to the optical fiber.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same direction. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, a first optical pump to provide optical power to the first optical fiber, and a second pump to provide optical power to both the first and the second optical fibers. By sharing the second pump between the first and the second optical fibers, a need to deploy additional pumps is alleviated. Scaling of the optical network to include additional optical fibers provides further cost savings by allowing more pumps to be shared among the multiple optical fibers.

Techniques for extending distributed acoustic sensing (DAS) range in undersea optical cables are provided. For example, DAS range can be extended by transmitting and amplifying a DAS signal along multiple spans of a first optical fiber, routing or bypassing the DAS signal from the first optical fiber to a second optical fiber different from the first fiber via a high-loss loopback architecture, and returning and amplifying the DAS signal along the same multiple spans back to a DAS device. The DAS device may then receive and process the DAS signal to detect any changes in the DAS environment. The loopback configuration may be based on different types of loopback architecture.