System design and optimization of optically amplified WDM-TDM hybrid polarization-insensitive fiber-opticMichelson interferometric sensor

In this paper, we investigate the optically amplified time-division-multipl exed (TDM) polarization-insensitive fiber-optic Michelson interferometric s ensor (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 pos t- and in-line cases can work successfully in the TDM-PIFOMIS system. The a mplitudes 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-PI-FOMIS system with an ex tinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4 x 10(-5) rad/(Hz)(1/2) at 1 kHz. For maintaining MP DS better than 3.4 x 10(-5) rad/(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 a nd -25 dBm, While employing such two post- and two in-line EDFA's in the TD M-PIFOMIS system, the allowable loss of the sensor array is 47 dB, We analy ze 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 min imize the PIIN and sensor crosstalk in the system. In order to reduce the s ystem 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.