In-line Amplifier Systems Research Articles

An approach for suppressing waveform distortion of SOAs by controlling the temperature on in-line optical amplifier systems

An approach for suppressing waveform distortion of SOAs by controlling the temperature on in-line optical amplifier systems

Suppression of the Cross-Gain Modulation in Remotely-Pumped EDF/DRA Hybrid Inline Amplifier Systems with Online OTDR for Gain Monitoring

Novel gain monitoring scheme in Remotely-Pumped EDF/DRA hybrid inline amplifier is proposed using Optical Time Domain Reflectometer (OTDR). Signal degradation due to cross gain modulation (XGM) caused by an OTDR pulse in the distributed Raman amplifier (DRA) section and remotely-pumped EDF (RP-EDF) unit is analyzed theoretically. The required conditions for suppressing of XGM in the DRA section are derived. We propose the directional bypass configuration to realize OTDR measurement without XGM in the EDF unit. Transmission experiments using the RP-EDF/DRA hybrid inline amplifier demonstrate the absence of transmission impairement induced by OTDR. An analysis of the OTDR trace for each gain medium is also discussed. The theoretical analysis agrees well with the experimental result.

Transmission distance of in-line amplifier systems with group-velocity-dispersion compensation

Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD. >

Automatic compensation technique for timewise fluctuating polarisation mode dispersion in in-line amplifier systems

An adaptive equaliser for polarisation mode dispersion (PMD) is developed, and its performance is evaluated in a 10 Gbit/s transmission system. This equaliser suppresses the power penalty due to PMD from 6.9 to 1.0 dB for a PMD value up to 65.7 ps. This result suggests the possibility of PMD compensation in multigigabit, 10000 km transmission systems.

In-line amplifier transmission distance determined by self-phase modulation and group-velocity dispersion

The propagation of an intensity-modulated signal in an optical fiber is numerically analyzed, taking self-phase modulation, group-velocity dispersion, and 2nd-order group-velocity dispersion into account. Transmission distances yielding a prescribed eye-opening penalty are shown to relate to three characteristic lengths: the dispersion length, the 2nd-order dispersion length, and the nonlinear length. These relations, with a slight modification for the signal power, are also found to be valid for in-line amplifier systems, in which each optical amplifier, though adding undesired amplified spontaneous emission, compensates the signal attenuation occurring in the preceding fiber. The resulting relations give us informative guidelines for designing such systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

System performance of coherent transmission over cascaded in-line fiber amplifiers

The limitations of cascaded in-line amplifier systems using coherent modulation-demodulation schemes are discussed by evaluating the product of the data rate and the transmission distance in terms of three different aspects: linear ASE accumulation, fiber chromatic and polarization dispersion, and phase noise caused by ASE through the Kerr effect. The linear ASE accumulation is shown to make the maximum value of the data rate-distance product proportionally increase with the ratio of the amplifier output signal power to the noise figure. It is also shown that the Kerr-nonlinearity-induced phase noise limits the product of the data rate and the third power of the distance, the maximum value of which is inversely proportional to both the amplifier output signal power and the noise figure

Evolution of field spectrum due to fiber-nonlinearity-induced phase noise in in-line optical amplifier systems

The spectral evolution of light propagating in in-line optical amplifier systems is investigated. Phase noise, which is caused by amplified spontaneous emission through the nonlinear Kerr effect, does not result in simple linewidth broadening but changes the lineshape of the Lorentzian carrier wave. Tails of the field spectrum are raised over a wide frequency range. It is experimentally confirmed that the phase noise is proportional to the third power of the number of amplifiers. Intensity-modulation direct-detection systems, in addition to coherent systems, are affected by the phase noise when a large number of amplifiers are cascaded. >

A noise-loading method for evaluating in-line amplifier systems

The authors propose a noise-loading method for evaluating inline optical amplifier systems. This method takes the linear accumulation of amplified spontaneous emission into account. Comparison against the measured performance of an experimental transmission system confirms that the method accurately simulates inline amplifier systems. The method can be used to evaluate transmitter-receiver pairs to be used in such systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>