Taichi Kogure

Pump light depolarization method for low PDG Raman amplification

In order to reduce polarisation dependence of gain (PDG) of Raman amplification, pump depolarization method with polarisation maintaining fibre (PMF) depolarizer is discussed. PMD of the depolarizer should be designed to optimum value determined by pump LDs longitudinal mode spacing.

Efficient Pump Depolarizer Analysis for Distributed Raman Amplifier With Low Polarization Dependence of Gain

This paper discusses a method of reducing the polarization dependence of gain (PDG) of a distributed Raman amplifier. Reducing its PDG is important for a Raman amplifier because it is higher than that of an erbium-doped fiber amplifier and can degrade transmission performance. Raman PDG is determined primarily by two factors, namely 1) polarization-mode dispersion (PMD) of the transmission fiber and 2) degree of polarization (DOP) of the pump source. The authors propose a simple analytical model to show the required pump light DOP for a given transmission fibers PMD and the allowable PDG. For instance, a low pump DOP of 5% produces a low PDG of 0.2 dB under typical fiber PMD conditions, in which the analytical model agrees well with experiment. Subsequently, to achieve the required DOP, the pump source configuration is investigated in detail. The authors used one length of polarization-maintaining fiber (PMF) as an efficient pump depolarizer and evaluated its performance for various pump light spectra. It has been shown that the DOP following the depolarizer is determined simply by Fourier transformation of the pump light spectrum. The analysis in this paper has led to the important result that a Fabry-Perot laser diode pump with a short piece of PMF is effective in achieving a low pump DOP due to its multimode spectrum when the length of the PMF is properly adjusted for the longitudinal-mode spacing frequency. It has been verified that a Raman amplifiers PDG can be reduced by the proposed efficient depolarizer sufficiently for a PDG-reduced Raman amplifier repeater to be applicable to long-haul transmission systems

65 /spl times/ 22.8 Gb/s WDM transmission over 8,398 km employing symmetrically collided transmission with Aeff managed fiber

Two proposed methodologies, Aeff management and symmetrically collided transmission, were discussed for long haul transmission systems. 65 /spl times/ 22.8 Gb/s WDM transmission over 8398 km was achieved by employing these techniques.

Polarization insensitive adaptive gain profile equalizer using variable Faraday rotators and walk-off crystals

We propose novel adaptive gain profile equalizer using variable Faraday rotators and walk-off crystal. Gain flatness of the EDFA with which it is used in a simple configuration is maintained to less than 1.2 dB over an input dynamic range of 10 dB.