The proposed amplifier structure and associated method of optical signal amplification efficiently utilizes the limited length of rare earth-doped optical amplifier. A multi-stage of amplification stages, which includes a first erbium-doped fiber amplifier stage pumped by a first pump light source and a second erbium-doped fiber amplifier stage pumped by a second pump light source, is provided and includes a split section disposed between the first and second amplification stages for splitting the amplified signal light into a C-band and a L-band; a reflector for reflecting the amplified output of the second amplifier stage back into the second amplifier stage and the first amplifier stage in a reverse direction; a combiner for combining the reflected output, in succession, from the second amplifier and first amplifier to produce an output signal; and, a circulator for redirecting the reflected output traveling in a reverse direction to the input of the combiner.

Wide band erbium-doped fiber amplifier (EDFA)

A wideband optical amplifier for amplifying an input optical signal of known wavelength in one of at least two bands of wavelength has a significantly small number of optical components and thus is low cost. The wideband optical amplifier includes: a first set of a first optical coupler, a first pump light source, and a first erbium doped optical fiber (EDF) which is excited by the first pump light source; an optical switch for changing an output signal of the first set; and a second set of a second optical coupler, a second pump light source, and a second EDF which is excited by the second pump light source. The first set amplifies a first band of optical signal while a series connection of the first set and the second set amplifies a second band of optical signal. In another aspect, a wideband variable wavelength optical source is achieved by utilizing the wideband optical amplifier described above within a closed loop.

Wideband optical amplifier and wideband variable wavelength optical source

A system and method is provided for minimizing power fluctuations and crosstalk in a wavelength division multiplexed optical (WDM) network employing dynamic add/drop techniques by utilizing amplifiers operating in a nearly linear region. Conventionally, erbium-doped fiber amplifiers (EDFAs) are operated in saturation for providing signal amplification in a WDM network. Instead of using saturated EDFAs, the present invention includes optical amplifiers operated in a linear or nearly linear regime for providing signal amplification in a dynamic add/drop or bursty data WDM network. By operating optical amplifiers in a linear or nearly linear regime, power fluctuations, transients and crosstalk caused by adding/dropping or switching channels in the WDM network are minimized. Raman amplifiers, EDFAs, or semiconductor optical amplifiers (SOAs) can all be operated in a linear or nearly linear range to provide linear amplification in such a dynamic add/drop or bursty data WDM network.

Dynamic add/drop of channels in a linear-optical-amplifier-based wavelength-division-multiplexed system

In order to obtain optical transmission equipment for wavelength division multiplexing for providing a small inter-wavelength deviation regardless of a change in an input level, an amplification band is divided with wavelengths at inflection points in a wavelength gain characteristic of an impurity-doped fiber. The equipment includes an optical filter unit and a optical gain adjusting unit. The optical filter unit obtains filter characteristics associated with wavelength gain characteristics for a plurality of input levels by changing a temperature thereof. The optical gain adjusting unit includes a wavelength gain characteristic shift filter having a Peltier element for controlling the temperate of the optical filter unit.

Filter with variable transmission character, optical transmission equipment and method of optical transmission

An inline repeater that uses a forward-pumped DRA that can use a pumping light source such as an FBG pumping light source and a fiber laser, which are the most commonly used, and an optical fiber communication system are realized. The optical fiber communication system comprises silica fiber as a gain medium for Raman amplification to amplify a signal light; a pumping light source that emits a pumping light that co-propagates through the silica fiber in the same direction as the signal light; and a multiplexer disposed between the silica fiber and the pumping light source that multiplexes the signal light and the pumping light, with the multiplexer being provided with a means to multiplex the signal light input thereto having a wavelength longer than the zero-dispersion wavelength of the silica fiber and the pumping light emitted from the pumping light source, and the pumping light source being equipped with a means to emit pumping light, with the longest wavelength of the pumping light being shorter than the shortest wavelength of the signal light by a frequency difference on the low-frequency side of 13.7 to 30 THz.

Inline Repeater and Optical Fiber Communication System

An optical amplifier is provided for performing amplification of optical signals of two wavelength bands, where deterioration in the optical SN ratio relative to one wavelength band is reduced, with a simple construction which can deal with restrictions on installation space, power consumption and the like. To this end, the present optical amplifier has a C/L band optical amplifying section for amplifying respective optical signals of a C band and an L band, a demultiplexer for demultiplexing output light from the C/L band optical amplifying section into the C band and the L band, an L band optical amplifying section for amplifying L band optical signals which have been demultiplexed by the demultiplexer, and a multiplexer for multiplexing the C band optical signals which have been demultiplexed by the demultiplexer and the L band optical signals which have been amplified by the L band optical amplifying section. The construction is such that a part of excitation light of a 1480nm band used in the C/L band optical amplifying section is supplied via an input terminal to a Raman amplification producing medium of a transmission path, and Raman amplified L band optical signals are input to the C/L band optical amplifying section.

Optical amplifier for C and L bands

An object is to provide a low cost optical amplifier having a simple construction where gain equalization of wavelength division multiplexed signal light, and the suppression of noise light is realized by a single optical device, and to provide a wavelength division multiplexed light transmission system using such an amplifier. Accordingly, the optical amplifier of the present invention is constructed by providing for a conventional optical amplifier incorporating an EDF, an excitation light source and a multiplexer, an optical filter having a periodic loss-wavelength characteristic with respect to a gain wavelength characteristic of the EDF. The optical filter has the characteristic that a spacing (FSR) corresponding to one period of a loss-wavelength characteristic corresponds to a gain peak wavelength difference of the EDF, and a maximum loss wavelength approximately coincides with a gain peak wavelength on a long wavelength side of the EDF. With such an optical filter, gain equalization of the signal light positioned in the gain peak wavelength neighborhood on the long wavelength side can be effected, and noise light generated in the gain peak wavelength neighborhood on the short wavelength side can be suppressed.

Optical amplifier and wave length division multiplexed light transmission system

A transmission apparatus being one of a plurality of transmission apparatuses included in a ring network, including: a processor configured to: receive a specified message from a first transmission apparatus, the specified message being for setting loopback for at least one wavelength in a ring network, the specified message being transmitted when a failure of at least one optical signal having the at least one wavelength is detected in a specified link of the ring network, and set a loopback to a switch, the loopback being set for a specified wavelength of the at least one wavelength when a specified optical signal having the specified wavelength is terminated by the switch and converted to an electrical signal and when the specified optical signal having the specified wavelength is not terminated and not converted to an electrical signal by any apparatus from a second transmission apparatus to the specified link.

Transmission apparatus and network control method

PROBLEM TO BE SOLVED: To provide an optical amplifier low in cost, simple in configuration and capable of realizing the gain equalization of a wavelength multiplex optical signal and the suppression of a noise light by a single optical device and to provide the wavelength multiplex transmission system using the optical amplifier. SOLUTION: This optical amplifier 10 is composed of an optical filter 4 with a periodic loss wavelength characteristic corresponding to a gain wavelength characteristic of an EDF 1 to a conventional optical amplifier provided with the EDF 1, a stimulation light source 2 and a synthesizer 3. The optical filter 4 has a characteristic where an interval (FSR) equivalent to one period of a loss wavelength characteristic corresponds to a gain peak wavelength difference of the EDF 1' and a maximum loss wavelength is nearly coincident with a gain peak wavelength toward the long wavelength of the EDF 1. This optical filter 4 applies gain equalization to a signal light placed around the gain peak wavelength toward the long wavelength side and a noise light produced around the gain peak wavelength towed a shorter wavelength is suppressed.

Optical amplifier and wavelength multiplex optical transmission system

Optical signals fed to the amplifier pass through a filter (4) and a multiplexer (3) receiving an excitation light input, and are then amplified in an erbium doped fiber (EDF) (1). The filter is arranged to have a wavelength-dependent insertion loss varying periodically over a predetermined spectral spacing, based on the wavelength difference between adjacent gain peaks introduced by the amplifier. The maximum loss wavelength of the filter approximately coincides with the gain peaks so as to flatten the overall transfer characteristic. An Independent claim is also included for a wavelength-division multiplexing (WDM) transmission system using optical amplifiers, at least one of which is of the type described by the invention.

Erbium doped fiber amplifier, for wavelength-division multiplexing transmission system, has optical filter with insertion loss characteristic chosen to flatten gain peaks introduced by amplifier

Naito Takao

Papers

Optical amplifier for C and L bands

Optical amplifier and wave length division multiplexed light transmission system

Transmission apparatus and network control method

Optical amplifier and wavelength multiplex optical transmission system

Erbium doped fiber amplifier, for wavelength-division multiplexing transmission system, has optical filter with insertion loss characteristic chosen to flatten gain peaks introduced by amplifier