An optical repeater is a C+L-band repeater inserted between a first transmission path fiber and a second transmission path fiber. The optical repeater includes: a first optical fiber amplifier inserted in a first line, for amplifying a C-band signal; a second optical fiber amplifier inserted in a second line, for amplifying an L-band signal; a third optical fiber amplifier inserted in a third line, for amplifying a C-band signal; a fourth optical fiber amplifier inserted in a fourth line, for amplifying an L-band signal; and a first loopback means provided between an input to the first optical fiber amplifier or an output from the first optical fiber amplifier and an input to the third optical fiber amplifier or an output from the third optical fiber amplifier.

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.

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.

Various example embodiments for supporting supervision in optical communication systems are presented. Various example embodiments for supporting supervision in optical communication systems may be configured to support supervision of an optical path including a remote optically pumped amplifier (ROPA) and, thus, supervision of the ROPA. Various example embodiments for supporting supervision of an optical path including a ROPA may be configured to support supervision of the optical path including the ROPA based on a pair of optical supervisory paths configured to extract a pair of optical supervisory signals from an optical path in a first direction and to insert the pair of optical supervisory signals into an optical path in a second direction. Various example embodiments for supporting supervision of an optical path including a ROPA may be configured to support supervision of the optical path including the ROPA based on a pair of optical time-domain reflectometer (OTDR) paths.

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.

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.

Various example embodiments for supporting supervision in optical communication systems are presented. Various example embodiments for supporting supervision in optical communication systems may be configured to support supervision of an optical path including a remote optically pumped amplifier (ROPA) and, thus, supervision of the ROPA. Various example embodiments for supporting supervision of an optical path including a ROPA may be configured to support supervision of the optical path including the ROPA based on a pair of optical supervisory paths configured to extract a pair of optical supervisory signals from an optical path in a first direction and to insert the pair of optical supervisory signals into an optical path in a second direction. Various example embodiments for supporting supervision of an optical path including a ROPA may be configured to support supervision of the optical path including the ROPA based on a pair of optical time-domain reflectometer (OTDR) paths.

An optical communication system is disclosed. The optical communication system may include a first fiber pump laser system having a first single mode (SM) fiber output configured to output a first pump laser radiation, a second fiber pump laser system having a second SM fiber output configured to output a second pump laser radiation, at least one combiner-splitter element configured to combine the first pump laser radiation and the second pump laser radiation and to transmit N portions of pump laser radiation, and N doped fiber amplifiers, where N is at least four, each doped fiber amplifier configured to receive one portion of the N portions of pump laser radiation and an input optical signal to be amplified, amplify the input optical signal into an amplified optical signal, and to transmit the amplified optical signal.

An optical repeater is a C+L-band repeater inserted between a first transmission path fiber and a second transmission path fiber. The optical repeater includes: a first optical fiber amplifier inserted in a first line, for amplifying a C-band signal; a second optical fiber amplifier inserted in a second line, for amplifying an L-band signal; a third optical fiber amplifier inserted in a third line, for amplifying a C-band signal; a fourth optical fiber amplifier inserted in a fourth line, for amplifying an L-band signal; and a first loopback means provided between an input to the first optical fiber amplifier or an output from the first optical fiber amplifier and an input to the third optical fiber amplifier or an output from the third optical fiber amplifier.