Signal Wavelength Effect on Overmodulation in Thulium Doped Fiber Amplifiers with Amplified Spontaneous Emission: A Simulink Pedestal

Abstract

Abstract Thulium-doped fiber amplifiers (TDFAs) can provide high power optical amplification in the wavelength range of 1,460–1,545 nm (S and near-C bands). They can be employed for dense wavelength division multiplexing (DWDM) in optical fiber communication over a broad range, unlike the Erbium-doped fiber amplifiers (EDFAs), which are active in the C-band only in the conventional “erbium window.” Line service surveillance and management of digital optical information in DWDM TDFA networks can be done by low-frequency amplitude modulation (~100 kHz) of TDFA pump and communication signal, termed as overmodulation. Governing equations for overmodulation gain dynamics in TDFAs using the Bononi and Rusch (1998) model was first derived in a companion paper (2017). The research provides a methodical test bed analysis using MatLab Simulink model with a different outlook in the respective field. The transfer functions for signal-to-signal and signal-to-amplified spontaneous emission were implemented to develop a simulator. An undesirable 30 % increment in the output modulation index at 8 dBm and 1,490 nm were obtained by simulating overmodulation sensitivity at different levels of mean input signal power and signal wavelength respectively at corner frequency. The optimum operating wavelength for TDFAs obtained was 1,490 nm.