Guodong Zhang

Distributed fiber Raman amplifiers with incoherent pumping

Distributed fiber Raman amplifier (DFRA) with incoherent pumping is investigated and its performance is compared to that with the conventional coherent pumping. It is shown that increasing the spectral bandwidth of incoherent pumping source can reduce the Raman gain ripple significantly, and degrade noise figure slightly at short wavelengths, compared to coherent pumping. To achieve the same gain flatness, the number of pumps for broad-band DFRAs with incoherent pumping can be significantly reduced compared to the coherent pumping.

Impact of fiber nonlinearity on PMD penalty in DWDM transmission systems

Polarization-mode dispersion (PMD) penalty measurement on a 10-Gb/s deployment-ready dense wavelength-division-multiplexing (DWDM) long-haul transmission system is reported in this letter. We investigate the impact of self-phase modulation (SPM) and cross-phase modulation (XPM) on PMD penalty in the DWDM system. It is confirmed that SPM can suppress the PMD penalty, and XPM-induced polarization-scattering in DWDM systems can reduce the PMD impairment a little bit further. Our measurements suggest that it is necessary to carry out the PMD penalty test on DWDM systems rather than back-to-back systems in order to accurately allocate transmission margin of the systems.

Noise statistics in optically preamplified differential phase-shift keying receivers with Mach–Zehnder interferometer demodulation

We report an analysis of the noise statistics for an optically preamplified differential phase-shift keying (DPSK) receiver with balanced and single-port detections. It is found that identical signal-amplified spontaneous emission beating noise exists for bits 1 and 0 in DPSK balanced detection. It is also revealed that the bit error ratio (BER) of a DPSK receiver with balanced detection has no direct relation to the conventional Q factor. Moreover, an analytic BER expression for the DPSK balanced detection receiver is presented.

Composite broad-band fiber Raman amplifiers using incoherent pumping.

This report presents an investigation of composite fiber Raman amplifiers (i.e., a distributed fiber Raman amplifier followed by a discrete fiber Raman amplifier) with in-coherent pumping, compared to conventional coherent pumping. It is shown that a flatter gain, noise figure and optical signal-to-noise ratio (OSNR) over 100-nm bandwidth can be achieved simultaneously by using two counter-incoherent pumps, compared to using six counter-coherent pumps. Moreover, it is found that a further improvement in gain, noise figure and OSNR flatness can be obtained in composite fiber Raman amplifiers with bi-directional incoherent pumping. The flatness of both gain and OSNR with a ripple of 1 dB is predicted by using one co-incoherent pump and one counter-incoherent pump.

Mean Relative Intensity Noise Transfer in Fiber Raman Amplifiers Using Multiple-Wavelength Pumps

We present a numerical analysis of mean relative intensity noise (RIN) transfer in a fiber Raman amplifier (FRA) using multiple-wavelength pumps. For the first time, the RIN transfer is investigated to include pump-to-pump and signal-to-signal RIN transfers, together with the ldquotraditionalrdquo pump, to signal transfer in a multiple-wavelength pumped FRA. We show that for a multiple-wavelength pumped FRA, pump-to-pump and signal-to-signal RIN transfers induce an increase of RIN transfer magnitude. For a multiple-wavelength counter pumped FRA, in additional to the major pump to signal RIN transfer, pump-to-pump RIN transfer is considerable, and signal-to-signal RIN transfer is very small. For a multiple-wavelength co-pumped FRA, both pump-to-pump and signal-to-signal RIN transfers increase RIN transfer magnitude significantly. In addition, for both a co- and counter pumped FRAs, particularly for the co-pumped FRA, the longer wavelength signals experience more RIN transfer than the shorter wavelength signals. Furthermore, the bandwidth of RIN transfer is significantly increased in a multiple-wavelength co-pumped FRA with multiple input signals compared to a single-wavelength co-pumped FRA with an input signal.

Employing slow polarization scrambling to improve performances for ultra-long haul DWDM systems

Using slow polarization scrambling to improve transmission performance simultaneously for multichannel of deployment ready DWDM system with reconfigurable OADM nodes is presented. It showed that the power fluctuation and maximum PreFEC BER can be reduced by using slow polarization scrambling.

Performance of distributed fiber Raman amplifiers with incoherent pumping

Distributed fiber Raman amplifier with incoherent pumping is investigated and the performance is compared to that with the conventional coherent pumping. Increasing the spectral bandwidth of incoherent pumping source will results in reduction of Raman gain linearly and gain ripple exponentially, and degradation of noise figure up to 1 dB, compared to coherent pumping with the same pump power.

Composite broad-band fiber Raman amplifiers by using incoherent pumping

This report presents an investigation of composite fiber Raman amplifiers, i.e. a distributed fiber Raman amplifier followed by a discrete fiber Raman amplifier, both with incoherent pumping, compared to conventional coherent pumping. It is shown that a flatter gain and optical signal-to-noise ratio (OSNR) over 100-nm bandwidth can be achieved by using two incoherent counter-pumps, compared to using six coherent counter-pumps. Moreover, it is also found that further flatter gain and flatter OSNR over 100-nm bandwidth can be obtained simultaneously in composite fiber Raman amplifiers with bi-directional pumping. The flatness of both gain and OSNR with a ripple of 1 dB is predicted by using one incoherent co-pump and one incoherent counter-pump.