In this paper, we investigate the optically amplified time-division-multiplexed (TDM) polarization-insensitive fiber-optic Michelson interferometric sensor (PIFOMIS) system using erbium-doped fiber amplifier (EDFA). The EDFA was named preamplifier, in-line amplifier or postamplifier, by the position it was located. We find that the preamplifier EDFA has limited usefulness because of its unstable amplification of the optical pulse trains. Both post-and in-line cases can work successfully in the TDM-PIFOMIS system. The amplitudes of the optical pulse trains are stable after amplified by the in-line EDFA, this is a significantly advantage of the optically amplified TDM-PIFOMIS system. The MPDS of the unamplified TDM-PIFOMIS system with an extinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4 10-5rad/(Hz)1/2 at 1 kHz. For maintaining MPDS better than 3.4 10-5rad/(Hz)1/2 at 1 kHz, the allowable worst ER for the post-and in-line amplified system are 20 and 17.8 dB, respectively,and the corresponding input signal peak power should be larger than -20 and -25 dBm. While employing such two post-and two in-line EDFA's in the TDM-PIFOMIS system,the allowable loss of the sensor array is 47 dB. We analyze the phase-induced intensity noise (PIIN) of the optically amplified TDM-PIFOMIS system in detail and propose methods to reduce the PIIN. The output optical pulse of an intensity modulator with high ER is a key issue to minimize the PIIN and sensor crosstalk in the system. In order to reduce the system PIIN, complexity and cost, we suggest an optimum optically amplified WDM (wavelength-division multiplexing)-TDM hybrid PIFOMIS system with four wavelengths and four eight-sensor subarrays.
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