A fiber-based optical amplifier is formed to exhibit a reflective architecture in a particular configuration where a single pump source is shared among several individual reflective amplifier elements. A passive, non-variable power splitter is used to direct sub-beams of sufficient power into the rare-earth doped fiber contained within individual amplifiers. Since the reflective architecture results in an optical signal passing through the doped fiber coil (gain medium) twice, a lower pump power (compared to a conventional single-pass structure) may be used to obtain the same target output power level and the single pump source is considered as sufficient to provide enough output power to pass through a power splitting arrangement and deliver enough pump power to provide amplification of a propagating optical signal in each of the individual amplifiers.

An amplification optical fiber operable to propagate light beams in a plurality of modes in a predetermined wavelength range through a core doped with a rare earth element, wherein Expression (1) is satisfied, where a cutoff wavelength of a propagated highest mode light beam is defined as max, under conditions in which the cutoff wavelength of the highest mode light beam is defined as c, a shortest wavelength of the wavelength range is defined as min, and a cutoff wavelength of a second-highest mode light beam to the highest mode light beam is min.

c>0.5 min+0.5 max(1)

According to an aspect of an embodiment, an optical amplification method may include identifying a first range of signal wavelengths that correspond to a first optical signal configured to propagate via an optical fiber. The method may further include generating a pumping signal having a range of pumping wavelengths, the range of pumping wavelengths based on a range of dispersion wavelengths, which correspond to the range of pumping wavelengths, not overlapping with the first range of signal wavelengths. The pumping signal may be provided to the optical fiber having the optical signal propagating thereon.

An optical amplifier that amplifies an incident WDM signal and includes cores having an amplification medium, the optical amplifier includes: a wavelength demultiplexer configured to demultiplex the incident WDM signal into wavelength bands and introducing the demultiplexed WDM signals into the cores separately; a wavelength multiplexer configured to multiplex amplified optical signals propagated through the cores and outputting the multiplexed signal; and an wavelength demultiplexing controller configured to monitor an amplification rate of a specific wavelength band of an amplified WDM signal or a scale associated with an amplification rate of a specific wavelength band, demultiplexing, from the incident WDM signal, an optical signal of a wavelength band having relatively-small optical amplification efficiency according to a monitoring result, and controlling demultiplexing performed by the wavelength demultiplexer in such a way as to amplify, with a relatively-large amplification rate, the optical signal of the wavelength band having relatively-small optical amplification efficiency.

To limit the number of excitation laser diodes (LDs) in an optical amplification device provided with a redundant excitation LD configuration, the optical amplification device is provided with: an excitation unit which outputs a plurality of excitation lights generated by a plurality of excitation light sources; a first distributing unit of which inputs are connected to the plurality of excitation light sources and which branches input lights and then outputs branched lights as a plurality of first distributed lights; a plurality of second distributing units of which inputs are connected to the first distributing unit and which combines and branches input lights and then outputs branched lights as a plurality of second distributed lights; and a plurality of gain mediums which are respectively excited by the plurality of second distributed lights.

According to an aspect of an embodiment, an optical signal and an optical pump signal may be obtained and multiplexed onto an erbium-doped optical fiber. The optical fiber may be configured to perform amplification of optical waveforms within a first wavelength range. Signal within the first wavelength range of the optical signal may be amplified using the optical fiber. In some embodiments, a bending radius of a bend in a fiber-based filter may be adjusted such that the filter is configured to attenuate signals in a second wavelength range in which the filter is configured to attenuate optical waveforms with respect to varying wavelength ranges depending on the bending radius of the bend in the filter. The second wavelength range may include wavelengths longer than the first wavelength range. The signals in the second wavelength range may be attenuated using the filter bent at the bending radius.

A device, system, and method for distributed Raman amplification of a multi-core fiber (MCF) is disclosed. The optical amplifier device includes a plurality of single mode optical pumps configured to supply one or more wavelengths to a depolarizer and a mode multiplexer configured to receive the one or more wavelengths from the depolarizer to output at least one combined depolarized optical light comprising the one or more wavelengths. The device also includes a coupler to couple the at least one combined depolarized optical light into MCF. The combined depolarized optical light Raman amplifies an optical signal in the MCF.

An assembly is used with an amplifier that amplifies light using source light, pump light, and a doped fiber. The assembly has a plurality of ports, including a first port for input of the source light, a second port for input of the pump light, a third port for output to the doped fiber, a fourth port for input from the doped fiber, and a fifth port for amplified output. A birefringent device in optical communication with each of the ports is configured to refract o-light and e-light components of the light passing therethrough with different refractive indices. For the first and fourth ports, a first half-wave plate in optical communication through the birefringent device is configured to rotate polarization of the light passing therethrough with a first rotation. For the second port, a second half-wave plate in optical communication through the birefringent device is configured to rotate polarization of the light passing therethrough with a second rotation different from the first polarization. A lens is used to focus the light, and an optical filter in optical communication with the lens is configured to reflect the pump light back to the lens and being configured to pass the source light. A rotator in optical communication with the lens is configured to rotate polarization of the light passing therethrough with a third rotation. The third rotation is half of the first rotation, and the first rotation is half of the second rotation. Finally, a wedge reflector in optical communication with the rotator is configured to reflect the light incident thereto. The source light and the pump light are combined and communicated from the second port for output to the doped fiber. Meanwhile, amplified light from the doped fiber is received at the fourth port and is communicated to the amplified output. Reverse light from the amplified output can be isolated from reaching the doped fiber, and reverse source light from the doped fiber can be isolated from reaching the source port.

Techniques for improving gain equalization in C- and L-band (C+L) erbium-doped fiber amplifier (EDFAs) are provided. For example, the C- and L-band amplification sections of a C+L EDFA may be separated and configured in a parallel arrangement or a serial arrangement. For both the parallel and serial arrangements, the C- and L-band amplification sections may share a common gain flattening filter (GFF) or each amplification section may include and employ a separate GFF. Moreover, in some examples, an interstage L-band GFF may be located before or upstream of the L-band amplification section such that the L-band optical signal is gain-equalized or flattened prior to the L-band amplification section amplifying the L-band.