Interferometric noise reduction through intrabit frequency evolution of directly modulated DFB lasers

A new technique is demonstrated that improves the performance of optical networks subject to interferometric noise. Every transmitter comprises a selected DFB laser that is NRZ ASK directly modulated with a large modulation depth. Under modulation, the center frequency of the DFB laser is found to v...

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Bibliographic Details
Published in:Journal of lightwave technology 1996-10, Vol.14 (10), p.2117-2125
Main Authors: Legg, P.J., Tur, M., Regev, H., Cornwell, W.D., Shabeer, M., Andonovic, I.
Format: Article
Language:English
Subjects:
Applied sciences
Crosstalk
Exact sciences and technology
Frequency
Laser noise
Noise reduction
Optical fiber networks
Optical filters
Optical interferometry
Optical noise
Optical signal processing
Optical transmitters
Systems, networks and services of telecommunications
Telecommunications
Telecommunications and information theory
Transmission and modulation (techniques and equipments)
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Summary:A new technique is demonstrated that improves the performance of optical networks subject to interferometric noise. Every transmitter comprises a selected DFB laser that is NRZ ASK directly modulated with a large modulation depth. Under modulation, the center frequency of the DFB laser is found to vary over the duration of each bit, falling during mark bits and rising during space bits with an exponential-like dependency of characteristic time constant /spl sim/20 ns. The optical frequency at the midpoint of each bit interval is not constant but depends upon the sequence of the preceding bits. Therefore, on the interference of a delayed-replica parasitic crosstalk waveform the interferometric noise generated on detection may be reduced by RF filtering according to the difference in center frequency of the interfering bits. This noise suppression which requires no additional hardware has been successfully modeled and experiment demonstrates little performance gain for a single interferer, as predicted. However, in the presence of multiple interferers significant improvement is predicted and observed at sub-Gb/s rates.
ISSN:0733-8724
1558-2213
DOI:10.1109/50.541198