Tunability of polarization-insensitive wavelength converters based on four-wave mixing in semiconductor optical amplifiers

TLDR

Optically transparent wavelength converters, which replicate the input wavelength at the output, are needed to enhance performance and simplify management in future mixed‑mode WDM networks, and four‑wave mixing in semiconductor optical amplifiers offers a tunable, polarization‑insensitive approach. This paper compares the output signal‑to‑noise ratios of three polarization‑insensitive FWM schemes in SOAs to assess their ultimate tunability. The authors employ a simple analytical model of FWM in SOAs to evaluate the three schemes under identical inputs and frequency shifts. The model predicts that the polarization‑diversity scheme achieves the highest output SNR and thus the greatest tunability among the three schemes.

Abstract

Optically transparent wavelength converters, in which the output is a wavelength-converted replica of the input, may be required to improve performance and ease management in future "mixed-mode" wavelength division multiplexed networks. Four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's) is an attractive optically transparent wavelength conversion technique because it allows pump tunability. So far, three schemes for polarization-insensitive FWM in SOA's have been demonstrated, using two copolarized pumps, two orthogonal pumps, and polarization diversity. This paper presents a comparison of their output signal-to-noise ratio, and hence their ultimate tunability. A simple analytical model for FWM in SOA's is used to predict that when each scheme has the same inputs and produces the same frequency shift, the polarization-diversity scheme has the highest output signal-to-noise ratio of the three schemes, and hence promises the greatest tunability.