383 results about "Raman amplification" patented technology

In a method for performing OTDR measurement in an optical transmission system including a first terminal station and a second terminal station, OTDR signal light is transmitted from an OTDR provided in the first terminal station to the second terminal station, in which the OTDR signal light is Raman amplified by using main signal light of the optical transmission system as pump light.

An optical amplifier with a flattened wideband response is obtained by coupling counter-propagating pumping energy into an optical waveguide to cause Raman amplification in the optical waveguide, and by reflecting an amplified signal received from the optical waveguide into an output waveguide using a reflector having a spectral characteristic that is complementary to the spectral gain characteristic of the Raman amplification.

The present invention provides a Raman amplifier and the like comprising a structure for keeping the flatness of power spectrum of Raman-amplified signal light. The Raman amplifier comprises an optical fiber for Raman-amplifying a plurality of signal channels of signal light having respective center optical frequencies different from each other; a pumping light supply section for supplying N (N being an integer of 2 or more) pumping channels of pumping light having respective center optical frequencies different from each other to the optical fiber; and a feedback section for detecting a part of the signal light Raman-amplified within the optical fiber when the pumping light is supplied thereto, and controlling the pumping light supply section such that the Raman-amplified signal light has a substantially flat power spectrum with respect to an optical frequency direction according to the result of detection. In particular, the feedback section divides the detected Raman-amplified signal light into N optical frequency ranges defined so as to include respective Raman amplification peaks as optical frequencies lower than respective center optical frequencies of the pumping channels of pumping light by an optical frequency shift of about 15 THz, and controls the pumping light supply section such that the Raman-amplified signal light has a power fluctuation of 2 dB or less in each of thus divided N optical frequency ranges.

An apparatus and method for measuring Raman-type spectra using optical dispersion to convert an optical spectrum into a waveform which can be detected directly in the time domain without the use of a conventional spectrometer. In the example of stimulated Raman spectroscopy, the apparatus and method exposes a sample to a chirped, pulsed probe beam and a Raman pump beam and the resulting Raman spectra is detected by an optical detector in the time domain, and analyzed. Alternatively, the Raman spectra from the probe and pump beams is chirped with a dispersive element prior to detection and analysis. Each probe pulse provides a snapshot of the Raman spectrum that is sampled in time so that neither repetitive waveforms nor static samples are required. Therefore, high speed acquisitions and high throughput assays can be conducted. To facilitate detection, these spectral signals can also be amplified using distributed Raman amplification directly in the dispersive element.

The invention discloses an optical fiber distributed disturbance sensor which comprises an optical fiber laser, a bidirectional distributed Raman amplification unit and a photoelectric detection and signal processing unit, wherein an output end of the optical fiber laser is connected with a first coupler; two output ends of the first coupler are respectively connected with an acoustic optical modulator and a third coupler; the bidirectional distributed Raman amplification unit is connected with the acoustic optical modulator by a first circulator and is connected with the third coupler by the first circulator; the photoelectric detection and signal processing unit is connected with the third coupler and used for receiving an interference-enhanced optical signal in the third coupler, converting the optical signal into an electric signal and carrying out subsequent data processing. In the optical fiber distributed disturbance sensor, the back scattering light intensity and the signal-to-noise ratio of the tail end of the optical fiber can be improved by the bidirectional distributed Raman amplification structure so as to improve the sensing distance of the optical fiber distributed disturbance sensor; and the light power received by a detector can be improved through the interference of a part of continuous light output by a light source and the back scattering light, so as to improve the signal-to-noise ratio of the system. The sensor is a combination of conventional photoelectric devices, has a simple structure and is easy to realize.

A Raman amplifier having a microstructured fiber and at least one pump laser, optically connected to one end of the microstructured fiber. The pump laser is adapted for emitting a pump radiation at a wavelength λ_p, and the microstructured fiber has a silica-based core surrounded by a plurality of capillary voids extending in the axial direction of the fiber. The core of microstructured fiber has at least one dopant added to silica, the dopant being suitable for enhancing Raman effect.

A method of Raman amplification comprising the step of effecting a plurality of pump wavelengths on a Raman-active transmission medium transmitting counter-propagating signal wavelengths, wherein at least one of said pump wavelengths are interleaved between said signal wavelengths.

A method of providing Raman amplification in an optical fiber sensing system, comprises generating a probe pulse of light and launching the pulse into a sensing optical fiber, generating pump light at a shorter wavelength and modulating it to produce a time-varying intensity profile, and launching the pump light into the sensing fiber. such that the intensity of the launched pump light during launch of the probe pulse is different from the intensity at other times. Raman amplification of backscattered light produced by the probe pulse as it propagates along the fiber is achieved, as is amplification of the probe pulse if the pump power is non-zero during launch of the probe pulse.

A method for pumping remote optically-pumped fiber amplifiers (ROPAs) in fiber-optic telecommunication systems is disclosed which uses cascaded Raman amplification to increase the maximum amount of pump power that can be delivered to the ROPA. According to the prior art, high power at the ROPA pump wavelength, λp, is launched directly into the fiber and the maximum launch power is limited by the onset of pump depletion by Raman noise and oscillations due to the high Raman gain at ˜(λp+100) nm. In preferred embodiments of the present invention, a ‘primary’ pump source of wavelength shorter than λp is launched into the delivery fiber along with two or more significantly lower-power ‘seed’ sources, among which is included one at λp. The wavelength and power of the seed source(s) are chosen such that, when combined with the high-power primary source, a series, n, where n≧2, of Raman conversions within the fiber ultimately leads to the development of high power at λp. In another embodiment, one or more of the seed sources at wavelengths shorter than λp are replaced by reflecting means to return, into the fiber, backward-travelling amplified spontaneous Raman scattered light resulting from high power in the fiber at a wavelength one Raman shift below the particular seed wavelength. In either case, the high power at λp is developed over a distributed length of the fiber, reaching its maximum some distance into the fiber and exceeding the maximum power possible at that point with the prior art.

A passive, coexisting 10 Gb/s passive optical network (XGPON) and Gb/s passive optical network (GPON) is created by using a pair of counter-propagating laser pump sources at a network-based optical line terminal, in combination with a feeder fiber, to create distributed Raman amplification for the upstream signals associated with both GPON and XGPON systems. A passive remote node is located at the opposite end of the feeder fiber, in the vicinity of a group of end-user locations, and includes a cyclic WDM and a pair of power splitters for the GPON and XGPON signals such that the GPON signals are thereafter directed through a first power splitter into optical network units (ONUs) specifically configured for GPON wavelengths and XGPON signals are directed through a second power splitter into ONUs configured for the XGPON wavelengths. The arrangement of the remote node allows for the reach and split ratios of the GPON and XGPON systems to be individually designed for optimum performance.

A commercially viable All-Raman system, is implemented by removing the dispersion compensating Fiber (DCF) and two stage amplifier at each span, and including a transmission path dispersion compensator which performs dispersion compensation on a transmission path basis. For example, by pre-compensating for the accumulated dispersion in the electrical domain at the transmitter, the gain of the Raman pumps at each span amplifier need only compensate for the loss within the span, without needing to compensate for the loss of a DCF. In addition there is provided a low-cost method for implementing a bidirectional Service Channel by modulating/demodulating low-rate data on the Raman pump. For example, a Raman amplifier can include an information source for producing a service channel signal which includes information to be communicated; and a modulator for modulating the Raman pump signal with the service channel signal.

The invention is in the field of distributed Raman amplification for digital and analog transmission applications and other applications, e.g., instrumentation and imaging applications, including HFC-CATV applications. In particular, the invention uses a high power broadband source of amplified spontaneous emission (ASE) as the Raman pump source for improved system performance. The invention also includes methods for constructing such a high-power broadband Raman pump.

The invention discloses a super-long distance phase-sensitive optical time domain reflectometer (Phi-OTDR) system, which comprises a Phi-OTDR demodulating system and detecting optical fiber, wherein a forward amplifying unit and a backward amplifying unit are respectively arranged at the front end and the back end of the detecting optical fiber. Detecting signal light of the Phi-OTDR system is amplified in a distributed manner by utilizing a bidirectional second-order or bidirectional multi-order Raman amplifying method, so that the uniformity of the intensity and the distribution of Rayleigh scattering signals on the whole optical fiber is further improved, the problem of the prior amplifying method of the Phi-OTDR system is effectively overcome, and the sensing distance of a single segment of detecting optical fiber of the Phi-OTDR system is further prolonged; and meanwhile, by utilizing bidirectional Raman amplifying multi-segment cascade connection, the super-long distance Phi-OTDR system which requires a low cost and has high performance can be realized. The method of the super-long distance Phi-OTDR system is helpful to improvements on the whole performance and the performance price ratio of the Phi-OTDR system during the application to long-distance safety monitoring of oil and gas transmitting pipelines, large-range peripheries, large-scale civil engineering structures, and the like.

A Raman laser system, the system comprising a resonator cavity comprising a plurality of reflectors, wherein at least one reflector is an output reflector adapted for outputting a pulsed output beam from the resonator cavity at a frequency corresponding to a Raman shifted frequency of the pump beam, wherein the output reflector is partially transmitting at the Raman-converted frequency; a solid state Raman-active medium located in the resonator cavity to be pumped by a pulsed pump beam having a pump repetition rate and for Raman-converting a pump pulse incident on the Raman-active medium to a resonating pulse at a Raman-converted frequency resonating in the resonator cavity; a resonator adjuster for adjusting the optical length of the resonator to match the round-trip time of the resonating Raman-converted pulse with the pump beam repetition rate such that the resonating pulse is coincident both temporally and spatially with a pump pulse in the Raman-active medium on each round trip, to Raman amplify the resonating pulse at the Raman-converted frequency in the Raman-active medium. Also a multiwavelength Raman laser system further comprising a dispersive element and a plurality of coupled resonator cavities. Also, methods for providing ultrafast pulsed Raman laser operation.

Raman amplification of a WDM signal with excellent gain flatness across a very large bandwidth is achieved. Co-propagating and counter-propagating Raman pumping are combined in the same fiber. Multiple pumping wavelengths are employed. Wavelengths employed for co-propagating pumping and wavelengths employed for counter-propagating pumping alternate in order of wavelength. In one embodiment, N co-propagating pump wavelengths and N+1 counter-propagating pump wavelengths are used. Alternatively, one may use N+1 co-propagating pump wavelengths and N counter-propagating pump wavelengths.

An optical transmission system capable of monitoring the operating status of Raman-amplifier repeaters even when an optical transmission line is partly disrupted by a fiber failure. An end station sends a monitoring command signal to request a particular repeater to report its operating status, together with a response carrier wave for use in that reporting. With their different wavelengths, an upstream wavelength selector in the repeater selectively passes the monitoring command signal while reflecting back the response carrier wave. Responsive to the command, a monitoring controller creates a response message containing operating status information. An excitation unit performs Raman amplification with a pump beam modulated by a modulation controller, so that the response message be superimposed on the response carrier wave propagating on the upstream link. The resulting monitoring response signal is routed from the upstream wavelength selector to a downstream optical coupler and sent back to the requesting end station.

An optical terminal apparatus includes a plurality of signal light units that transmits and receives a signal light having a predetermined wavelength; at least one pumping light unit that emits a pumping light having a predetermined wavelength to perform Raman amplification for the signal light transmitted; and an optical multiplexer/demultiplexer that multiplexes/demultiplexes the signal light and the pumping light, the optical multiplexer/demultiplexer having one end connected to an optical transmission path and other end connected to the signal light units and the pumping light unit.

An optical fiber transmission link has a first optical fiber with a high effective area coupled to a second, downstream optical fiber with a low effective area. The downstream fiber has non-zero dispersion and low dispersion slope. Characteristics of the upstream fiber permit the launching of high power channels in a wavelength division multiplexing, and characteristics of the downstream fiber enable Raman amplification along that fiber to extend the transmission distance before a need for discrete amplification. The downstream fiber has a non-zero dispersion in the C-band wavelengths and a low dispersion slope and has low attenuation at the signal and pump wavelengths. Refractive-index profiles include variations of W-type fibers that may include outer rings of positive or negative index. Pumping of the downstream fiber may occur either co-directionally to the signals, counter-directionally to the signals, or in both directions.

The invention relates to a multi-fiber core single-mode optical fiber and a manufacturing method thereof. The multi-fiber core single-mode optical fiber comprises claddings and a plurality of fiber cores. The multi-fiber core single-mode optical fiber is characterized in that the fiber cores include a pumping fiber core and a plurality of signal fiber cores, wherein the pumping fiber core is arranged in the center of the optical fiber, the signal fiber cores are distributed on one to three circumferences around the center at equal intervals, so as to form one to three layers of signal fiber cores, sunken claddings tightly cover each signal fiber core, and common claddings are arranged outside the sunken claddings. The multi-fiber core single-mode optical fiber has the characteristics of low signal crosstalk among all of the signal fiber cores, easiness in online light amplification, simplicity and convenience in manufacturing and low manufacturing cost and is suitable for large-scale production. A distributed Raman amplification technique of the multi-fiber core single-mode optical fiber is used in an ultrahigh-speed communication system, so that effective light amplification can be realized, and the harm of a non-linear effect to the performance of a high-speed optical transmission system is further reduced.

The present invention relates to an all-optical-fibre adjustable bandwidth continuous spectrum laser pump source (FBCSL) for ultraflat wideband Raman amplification, belonging to the field of high-speed wideband optical fibre communication technology. It adopts a high optical non-linear optical fibre (HNL-DSF) with approaching flat zero dispersion characteristics at Raman laser wavelength place as gain medium, and on the two ends of the above-mentioned HNL-DSF) a wideband reflector can be connected to form all the optical fibre Fabry-Perot (F-P) adjustable bandwidth continuous spectrum Raman laser or a wideband wavelength division multiplexing optical fibre coupler is connected to form all-optical-fibre circular cavity adjustable bandwidth continuous spectrum Raman laser.

Optical service channel (OSC) systems and methods over high loss links are described utilizing redundant telemetry channels. A first telemetry channel provides a low bandwidth communication channel used when Raman amplification is unavailable on a high loss link for supporting a subset of operations, administration, maintenance, and provisioning (OAM&P) communication. A second telemetry channel provides a high bandwidth communication channel for when Raman amplification is available to support full OAM&P communication. The first and second telemetry operate cooperatively ensuring nodal OAM&P communication over high loss links (e.g., 50 dB) regardless of operational status of Raman amplification.

Optical fibers with high non-linearity and low dispersion suitable for the Raman amplification are offered. Their structural and characteristic specifics are as follows: first core 1 with α profile surrounded with second core 2, further second core surrounded with cladding 5; setting first core 1 for no less than 1.8% of relative refractive index difference from cladding 5; setting second core 2 for no more than −0.4% of relative refractive index difference from cladding 5, setting α for 1.5 or larger, making second core 2 at least 2.2 times as large as first core 1 in diameter; and an effective area of no more than 15 μm², a dispersion slope of 0.05 ps/nm²/km or lower in absolute value, a dispersion of no less than 5 ps/nm/km and no more than 20 ps/nm/km, in absolute value, a cutoff wavelength of 1350 nm or shorter, and a bending loss of 5.0 dB or lower in a bending diameter of 20 mm, each at a wavelength of 1.55 μm.