Pulsed Lightwave Frequency Synthesizer System Using an EDFA and AOD in a Fiber Loop

Kazuo AIDA  Kiyoshi NAKAGAWA  

IEICE TRANSACTIONS on Communications   Vol.E78-B   No.5   pp.664-673
Publication Date: 1995/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Optical Signal Processing and Its Applications to Telecommunications)
lightwave frequency synthesizer,  EDFA,  AOD,  fiber loop,  

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We report here a pulsed lightwave frequency synthesizer system that is composed of a pulsed lightwave sweep frequency generator and a tracking generator. The key advance in the sweep generator is the use of a dynamically gain controlled EDFA. The combination of feedback and feed forward dynamic gain control effectively compensates EDFA gain fluctuation and equalizes fiber loop loss so that the initial pulse wave form and amplitude is retained in the loop at large circuit numbers. Over 1000 pulsed lightwave frequencies are synthesized in 250MHz steps by the sweep generator. Almost flat response (0.55dB variation) is realized up to 240GHz. The power spectrum decreases by 67% (1.7dB down) at 250GHz. The peak level of the pulses output from the loop is about -4dBm. Tracking generator and total synthesizer system performance are evaluated by (a) beat frequency between the tracking generator and the master lightwave source, (b) beat frequency between two tracking generators, and (c) a frequency chain between the master lightwave source and another HCN stabilized lightwave source via the synthesizer system. A continuous lightwave frequency locked to a frequency selected from the pulsed sweep frequency signal is demonstrated at over 200GHz to have an instability of 5MHz. Absolute accuracy of the lightwave frequency emitted from the synthesizer system is about 10MHz. Therefore, the relative accuracy of the lightwave frequency is as high as 510-8.