Modified NOLM for Stable and Improved 2R Operation at Ultra-High Bit Rates

Shin ARAHIRA  Hitoshi MURAI  Yoh OGAWA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E89-B   No.12   pp.3296-3305
Publication Date: 2006/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.12.3296
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fiber-Optic Transmission for Communications
Keyword: 
all-optical signal processing,  2R regeneration,  OTDM systems,  optical nonlinearities in optical fiber,  sagnac interferometer,  

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Summary: 
A nonlinear optical fiber loop mirror (NOLM) adapted for all-optical 2R operation at ultrahigh bit-rates was experimentally and theoretically investigated. The proposed NOLM was created by adding inline/external fiber polarizers and also an inline optical phase-bias compensator (OPBC) to a standard NOLM. A theoretical investigation revealed that the operation of the standard NOLM became unstable due to residual polarization crosstalk of the polarization-maintaining optical components making up the NOLM, and that it could be dramatically improved with the inline/external polarizers. The NOLM with the polarizers ensured stable switching operation with high switching-dynamic-range (>30 dB) against the change of the wavelength of the input clock pulses, and the change of the environment temperature. We also experimentally verified that the OPBC played a dramatic role to ensure excellent dynamic switching performance of the NOLM, and to achieve signal-Q-recovery of the regenerated signals. All optical 2R experiments at 40 Gb/s and 160 Gb/s were performed with the modified NOLM. Signal regeneration with improved extinction ratio and signal Q value was successfully demonstrated. Q-recovery to the input of the control pulses degraded with ASE noise accumulation was also successfully achieved.