摘要:
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.
摘要:
A modular interleaved Raman amplifier structure is exploited to reap the advantages provided by the high Raman gain coefficient and small effective area of highly nonlinear fibers without incurring penalties caused by nonlinear effects and double-Rayleigh backscattering noise. Very tight WDM channel spacings may be accommodated. The amplifier structure may be implemented at very low initial cost and with high reliability, scalability, and modularity.
摘要:
An advantageous amplification architecture for DWDM systems including systems with very high capacity is provided. A modular interleaved structure for amplification is provided. Advantages include robustness to non-linear effects, modular as-needed deployment of system capacity, and low noise figure in implementations that incorporate Raman amplification technology.
摘要:
An optical amplifying unit (100; 100′) for amplifying optical signals in an optical transmission system has an amplification wavelength band with a lower wavelength limit greater than 1570 nm and includes an input (101) for the input of optical signals, an output (102) for the output of optical signals and an optical amplifier (104) interposed between the input (101) and the output (102) to amplify the optical signals. The optical amplifier (104) includes an amplification fiber (108) co-doped with erbium and ytterbium, at least a pump source (109, 110) to generate pump radiation and at least an optical coupler (111, 112) optically coupling the pump sources (109, 110) to the amplification fiber (108). The optical amplifying unit has a power gain of at least 31 dB when the optical signals have an input power of at least −10.5 dBm and wavelengths within the amplification wavelength band.
摘要:
A looped WDM optical network comprises an optical loop with optical amplifiers (12,16) between the sections of the loop (11) and with ASE recirculation in the loop. At a point of the loop a laser beam is injected and allowed to circulate in the loop with the laser beam being centered around a λLINK wavelength where it is desired that a lasing peak be generated. This supplies high network strength in terms of section loss variations and greatly improves the OSNR of the WDM signal. High network survivability is also achievable.
摘要:
An approach for minimizing four-wave mixing (FWM) cross-talk (XT) in a WDM (wavelength division multiplexing) optical communication system is disclosed. An Erbium doped Fiber Amplifier (EDFA) includes a pre-amplifier that receives an input optical signal and outputs an amplified input optical signal. The pre-amplifier includes the following components: a first active fiber that carries WDM signals corresponding to a particular operating band (e.g., L-band); a co-propagating pump laser that induces high inversion in a portion of the first active fiber; a filter that is coupled to the first active fiber and slightly inverts the gain tilt of the WDM signals and suppresses the amplified spontaneous emission (ASE) lights accumulated at wavelengths shorter than the signal bandwidth; a second active fiber that is coupled to the filter; and a counter-propagating pump laser that induces high inversion in a portion of the second active fiber. An optical unit (e.g., an optical add/drop module, a gain equalizing filter (GEF), or a dispersion compensating fiber (DCF)) may be coupled to the pre-amplifier and receives the amplified input signal, in which the optical unit introduces a prescribed loss to the WDM system. A booster amplifier is coupled to the optical unit and is configured to amplify a signal that is output from the optical unit. An automatic optical gain control (AOGC) mechanism of the EDFA provides nearly constant gain that is independent of the number of channels utilized in the WDM system and also minimizes system penalties due to fast relaxation oscillations induced by adding/dropping of channels.
摘要:
An optical transmission system includes an optical transmitting unit (10) to transmit optical signals in a transmission wavelength band above 1570 nm; an optical receiving unit to receive the optical signals; an optical fiber link optically coupling the transmitting unit to the receiving unit, at least an optical amplifying unit (100) coupled along the link and adapted to amplify the optical signals; the optical amplifying unit (100) having an amplification wavelength band including the transmission wavelength band and comprising: an input (101) for the input of the optical signals, an output (102) for the output of the optical signals, at least an erbium-doped active fiber (103a, 103b) for the amplification of the optical signals, having a first end optically coupled to the input (101) and a second end optically coupled to the output (102), a pump source (104, 106) for generating a pump radiation having a wavelength greater than 1400 nm and lower than 1470 nm, and an optical coupler (105, 107) optically coupling the pump source (104) to the active fiber (103a, 103b).
摘要:
A Raman amplifier structure (121, 221) for optically amplifying an input optical signal comprises an optical means (22) through which the optical signal is propagated, a first pump optical source (10) for generating a first pump radiation and at least one second pump optical source (24, 27) for generating a second pump radiation. The first and second pump optical radiations are combined and propagated in optical transmission means (22) for supplying an optical amplification of the signal through the Raman effect. The first pump optical source (10) comprises a first laser source (12) for generating a radiation with relatively low noise and relatively low power and a Raman amplifier (13) for amplifying the radiation coming from the first laser source for generating the first pump radiation. The Raman amplifier (13) comprises a second laser source (14) for generating an optical radiation having relatively higher power and noise than the first laser source and the radiation coming from the second laser source is used for counter-pumping the radiation coming from the first laser source (12) for generating the first pump radiation. This limits the amount of noise transferred from the second source (14) to the first pump radiation.
摘要:
A looped WDM optical network comprises an optical loop with optical amplifiers (12,16) between the sections of the loop (11) and with ASE recirculation in the loop. At a point of the loop a laser beam is injected and allowed to circulate in the loop with the laser beam being centered around a λLINK wavelength where it is desired that a lasing peak be generated. This supplies high network strength in terms of section loss variations and greatly improves the OSNR of the WDM signal. High network survivability is also achievable.
摘要:
A Raman pump module for generating pump radiation having a pump wavelength (λp) for coupling into a transmission fiber of an optical wavelength division multiplex (WDM) communication system to provide Raman amplification of WDM radiation counter propagating therethrough is disclosed. The pump module is for use in a communications system in which the WDM radiation has a transmission waveband (λs) and wherein the transmission fiber has a zero dispersion wavelength (λm) lying midway between the transmission waveband and the pump wavelength. The module comprises a Raman pump laser for generating the pump radiation and a de-correlator for de-correlating the longitudinal modes of the pump radiation before it is coupled into the transmission fiber.