Abstract
A phase-sensitive amplifier (PSA) has the potential of low-noise optical amplification and nonlinear phase noise mitigation. For PSA operation, the chromatic dispersion (CD) that causes gain ripple must be compensated before amplification. We propose an accurate CD estimation method for non-degenerate PSAs (ND-PSAs). We experimentally demonstrated its effectiveness by using periodically poled LiNbO3 waveguides as amplification mediums. We first modified the conventional formula for the gain spectrum under residual CD conditions to be applicable to ND-PSAs by considering phase locking. We then experimentally described the effect of passband narrowing due to the gain ripple on the signal quality using a probabilistically shaped 64QAM signal. Furthermore, we applied the modified formula to CD estimation and compensation. As a result, accurate CD estimation on the sub-ps/nm order and gain-flattened spectrum over 3.5 THz were demonstrated with our method. We also propose a method for estimating residual CD from the gain variation among wavelength division multiplexing (WDM) channels. The possibility of adaptive compensation for CD was shown by carrying out WDM amplification.
Highlights
O PTICAL transport networks using wavelength division multiplexing (WDM) have been widely deployed
We experimentally investigated that the chromatic dispersion (CD) tolerance in an ND-phase-sensitive amplifier (PSA) for a single channel depends on the symbol rate and Δf
We investigated the impact of residual CD on non-degenerate PSAs (ND-PSAs) and proposed an accurate CD estimation method toward wideband phase-sensitive amplification
Summary
O PTICAL transport networks using wavelength division multiplexing (WDM) have been widely deployed. In repeated-amplification transmission, the OSNR is restricted by the fiber loss and the noise figure (NF) of optical amplifiers. We investigated the impact of residual CD on signal quality and proposed a method estimating the residual CD from gain spectrum of ASE light [20]. We discuss that work in more detail regarding the correspondence between theory and experiment and propose another CD estimation method using gain variation among WDM channels. This method can adaptively track CD variation due to environmental factors such as temperature fluctuation. We conducted a fundamental demonstration of this proposed method through an WDM-amplification experiment and show the detailed characteristics of estimation accuracy through numerical simulations
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