184 results about "Raman pump" patented technology

An approach for automatic Raman gain and tilt control for a WDM (Wavelength Division Multiplexing) optical communication systems is disclosed. An optical fiber carries a plurality of optical signals, in which at least one of the optical signals are reference signals. An optical gain unit (e.g., Raman pump unit) couples to the optical fiber and adjusts the reference signals to compensate, in part, for losses associated with the optical fiber and gain tilt accumulation. Upon detecting and analyzing the reference signals, a controller controls the optical gain unit and outputs a control signal to the optical gain unit based upon the analyzed reference signals. An optical amplifier is connected to the optical fiber and amplifies the optical signals. The optical gain unit provides a nearly constant power per channel at an input of the optical amplifier. Under this approach, a Raman gain control mechanism, combined with the use of gain controlled EDFA (Erbium Doped Fiber Amplifier), allows high transmission capacity over ultra-long distances without optical regeneration and with high flexibility.

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.

An object of the present invention is to prevent an interruption circuit of an optical amplifier from malfunctioning due to Raman pump wave. A typical mode of the present invention is characterized in that an pump wave elimination filter is inserted before an input-light detector and a reflected-light detector which constitute the optical amplifier. This permits only a signal component to be detected, enabling interruption operation, while eliminating a remaining component of Raman pump wave transmitted from for example a downstream of an optical fiber transmission line. In addition, a judgment threshold value for the interruption operation is changed according to ON/OFF condition of the pump wave. Or the Raman pump wave itself is used for detecting output's open.

The invention discloses an optical fiber Brillouin optical time domain analyzer, which is made based on optical fiber broadband nonlinear light amplification effect and strain, temperature effect and optical light domain analysis principle of coherent amplified Brillouin scattering. The optical fiber Brillouin optical time domain analyzer comprises a narrowband single-frequency fiber laser, a fiber beam splitter, a pulse modulator, two optical fiber circulators, a heterodyne receiver, a digital signal processor, a fiber-grating filter, a monomode fiber and a continuous-operating fiber Raman pump laser. The continuous-operating high-power fiber Raman pump laser is used as the pump light source of the Brillouin optical time domain analyzer, which can overcome the difficulty in strictly locking the frequency of a detection laser and the pump laser of the Brillouin optical time domain analyzer; and boardband fiber nonlinear scattering amplification is used for substituting for narrowband Brillouin amplification to increase the gain of stimulated Brillouin scattering with back amplification, thus improving the S/N ratio of the system, increasing the measurement length, and improving the accuracy for simultaneous measurement of stain and temperature.

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 Brillouin optical time domain analyzing and sensing system based on ultra-long annular laser pumping. The Brillouin optical time domain analyzing and sensing system based on the ultra-long annular laser pumping comprises first-order raman pump light (16) with the wavelength of 13 xxnm, a wavelength division multiplexer WDM pair (17) and a sensor fiber (18), wherein the wavelength division multiplexer and the sensor fiber form an ultra-long distance annular laser resonant cavity, the first-order raman pump light is fed back by the annular laser resonant cavity to generate lasing light with the wavelength of 14 XXnm. The lasing light with the wavelength of 14 XXnm performs second-order raman amplification on probe light with wavelength of 15 XXnm and Brillouin pumping. In comparison with a Brillouin sensing system based on linear cavity amplification, sensing signals are distributed more smoothly along the optical fiber, and the consistency of sensing quality in the whole process is remarkably improved; noise transfer of pumping-signal relative strength can be effectively suppressed, and temperature, spatial resolution of strain detection and measurement accuracy can be substantially improved; due to the fact that an extra second-order pump light source does not need to be added, substantial stretching of the sensing distance is obtained with low cost, and the Brillouin optical time domain analyzing and sensing system based on the ultra-long annular laser pumping has certain practicability.

A long-distance polarization and phase-sensitive reflectometry based on random laser amplification for extending a sensing distance includes a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by unilateral pumps, a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by bilateral pumps, and a long-distance polarization and phase-sensitive reflectometry of a Raman amplification based on a combination of optical fiber random lasers generated by unilateral pumps and a common Raman pump source, which are applied in optical fiber perturbation sensing and have a capability of greatly improving a working distance of a sensing system and a high practicability.

A submarine optical repeater includes a submarine amplifier module, which further includes a pumping laser module and an optical detector module. The pumping laser module generates optical amplifications within an optical cable, and, in the case of a fault in the optical cable, the optical detector module detects at least one characteristic of an optical signal caused by the fault in the optical cable. This configuration then identifies a particular signal characteristic that indicates a fault within the optical cable.

An arrangement for providing real-time, in-service OTDR measurements in an optical communication system utilizing distributed Raman amplification. One or more of the laser diodes used to provide the pump light necessary to create optical gain is modified to also generate short duration pulses that ride above or below the conventional pump light. These short duration pulses (which co-exist with the pump light within the optical fiber) are used in performing OTDR measurements, with a conventional processing system used to evaluate reflected pulses and create the actual OTDR measurements.

The invention discloses a method and system for improving sensing performance of a long-distance Brillouin optical time domain analysis system. On the basis of the existing long-distance Brillouin optical time domain analysis system which uses a first-order Raman amplification technique, a pair of optical fiber gratings with peak reflectivity being larger than 80 percent and consistent central reflection wavelength are fused on the two sides of sensing optical fibers to form a long-distance laser resonant cavity. Laser generated by the laser resonant cavity is used as a second-order Raman pump and a first-order Raman pump to simultaneously take an effect of amplifying sensing signals. Compared with a Brillouin sensing system which is based on the first-order Raman amplification, under the conditions of the same pump power, the method and the system provided by the invention have the advantages that higher grains can be obtained and the pump efficiency is improved; the sensing signals are distributed more smoothly along the optical fibers; when the system is used for long-distance temperature/stress sensing, the spatial resolution, the measurement accuracy and the sensitivity of the monitoring system can be greatly improved; and the sensing performance is obviously improved at a low cost without increasing an additional second-order pump light source.

The present invention aims at providing a method for controlling wavelength characteristics of optical transmission powers by Raman amplification, in which the wavelength characteristics of optical transmission powers are automatically compensated without giving any losses to channel lights to thereby improve transmission characteristics, and an apparatus adopting the same. To this end, the method for controlling wavelength characteristics of optical transmission powers by Raman amplification according to present invention supplies Raman pump light to an optical transmission path (Raman amplifying medium); compensates the wavelength characteristics of optical transmission powers caused by transmission of WDM signal light through the optical transmission path, by gain wavelength characteristics of generated Raman amplification; and monitors the wavelength characteristics of optical transmission powers after Raman amplification to thereby control the gain wavelength characteristics of Raman amplification.

The invention discloses a non-relay optical fiber transmission system and method. The non-relay optical fiber transmission system comprises the following components that are sequentially connected with one another by transmission optical fibers: an optical transmitter, an optical power amplifier, an optical pulse expander, an optical fiber, a high-power optical fiber amplifier, a chromatic dispersion compensation module, an optical pulse compressor, a remotely-pumped optical preamplifier, a distributive optical fiber Raman amplifier, an optical preamplifier, a nonlinear optical loop mirror and an optical receiver. The remotely-pumped optical preamplifier is connected with a remotely-pumped source; and the distributive optical fiber Raman amplifier mainly consists of a Raman pumping source, a wavelength division multiplexer and an optical signal transmission fiber arranged behind the remotely-pumped optical preamplifier. In the invention, a linear chirped fiber grating is used for carrying out time-domain broadening on picosecond optical pulse; the picosecond optical pulse is amplified by the high-power amplifier and is transmitted in the optical fiber; the reversely arranged linear chirped fiber grating is used for compressing the time-domain expanded pulse and recovering the time-domain expanded pulse as the picoscond pulse, thus obtaining time spread gain, thereby leading the transmission distance of the non-relay optical fiber transmission system to be extended.

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 present invention is directed to a system and method which provide a Raman pump which is spectrally tailored in response to feedback from control structure associated with the Raman pump source. In certain embodiments of the present inventions, an incoherently beam combined laser (IBC) is utilized to provide a spectrally tailored Raman pump. In these embodiments, emitters in an emitter array are either individually addressable or block addressable to facilitate adjustment of emitter output power. By adjustment of the output power, the Raman pump may be spectrally tailored. The spectral tailoring can occur by employing suitable control algorithms to algorithms to dynamically maintain reasonably flat Raman gain.

The present invention discloses an optical line terminal that includes one or more downstream signal processing means for generating a downstream signal, and converting data of the downstream signal into a serial data; a wavelength division multiplexing means for combining the serial data of different wavelengths together and then performing transmission of the combined signals; and one or more upstream signal processing means for extracting data of an upstream signal from the wavelength division multiplexing means. The terminal includes an extender including a first optical amplifier for amplifying the upstream signal, a second optical amplifier for amplifying the downstream signal, a Raman wavelength division multiplexing module for separating and combining data signal and pump light from Raman pump unit, and a Raman pump unit coupled to the Raman wavelength division multiplexing module to provide Raman amplification to the upstream and downstream signals.

A system and method for providing eye-safety protection during operation of distributed Raman amplifiers based on the application of continuous out-of-band amplified spontaneous scattering (ASS) monitoring in an optical communication network span coupled to the Raman amplifier, and real-time detection and analysis of changes in the monitored ASS power level, The system includes at least one Raman pump for introducing Raman energy into the span, a monitoring unit for performing the continuous ASS monitoring, and a control unit operative to detect and analyze in real-time changes in the ASS power, and upon determination that such changes indicate an open span, to reduce the level of the Raman pump energy entering the span to a safe level.

The invention relates to a low-noise remote pump EDFA. The low-noise remote pump EDFA comprises a passive gain unit, an optical cable part and a pump unit part; the passive gain unit is formed by connecting a first optical isolator ISO1, a first wavelength division multiplexer WDM1, a first erbium doped fiber EDF1, a second wavelength division multiplexer WDM2, a second optical isolator ISO2, a gain flattening filter, a third wavelength division multiplexer WDM3, a second erbium doped fiber EDF2, a dichroic mirror and an optical isolator ISO3 in sequence; a pump source is formed by combining an EDFA pump source with a Raman pump source, the Raman pump source is used for amplifying the EDFA pump source, the purpose that pump power injected into the passive gain unit does not change or even is higher under the condition of relative small power of the EDFA pump source is achieved, the non-relay optical transmission distance is prolonged, no cable needs to be laid in the long-distance optical communication optical cable laying process, the laying cost and maintaining cost of circuits are reduced, peak power in the optical cable is reduced, safety of the optical cable is improved greatly, and the maintaining cost of the optical cable is reduced greatly.

The present invention provides methods and apparatuses for controlling a gain of an optical fiber amplifier. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump. The dynamic gain control technique is applicable to an Erbium-doped fiber/waveguide amplifier. Also, a dynamic gain control technique controls a backward-pumped Raman amplifier, in which the power variation is determined at one geographical location and the optical pumps are controlled at another geographical location.

The invention provides an optical fiber gas cascaded Raman laser capable of realizing 3-5-micron band tuning. The laser comprises a 1-micron band tunable Raman pump source, a first level gas Raman laser generation device and a second level gas Raman laser generation device, the first level gas Raman laser generation device converts 1-micron pump laser generated by the 1-micron band tunable Raman pump source into first level Raman scattering laser, and the first level Raman scattering laser is laser of 1.5-micron band or 2-micron band; and the second level gas Raman laser generation device converts the first level Raman scattering laser into second level Raman scattering laser, and the second level Raman scattering laser is 3-5-micron band tunable mid-infrared laser. According to the optical fiber gas cascaded Raman laser provided by the invention, the output of 3-5-micron band tunable mid-infrared laser is realized in an anti-resonant hollow fiber with a negative curvature by employing a gas Raman cascading manner for the first time.

In a one-fiber bidirectional optical transmission system in which output optical signals of optical transmitter-receivers respectively connected to the opposite ends of one optical fiber transmission line are bidirectionally transmitted in the optical fiber transmission line, which utilizes a Raman amplification effect by backward pumping, a frequency satisfying the conditions of |f_s1−f₀|≠|f_p2−f₀| and |f_s2−f₀|≠|f_p1−f₀| is selected, where f₀ is a zero dispersion frequency of the optical fiber transmission line, f_s1 and f_s2 are the frequencies of the first signal and the second signal, respectively, and f_p1 and f_p2 are frequencies of the first Raman pump light and the second Raman pump light, respectively.