Repetition rate requirements for time-division multiplexed Raman pumping

• Published in: Journal of lightwave technology 2004-02, Vol.22 (2), p.401-408
• Main Authors: Winzer, P.J., Bromage, J., Kane, R.T., Sammer, P.A., Headley, C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cascading; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fiber lasers; Gain; Integrated optics. Optical fibers and wave guides; Laser tuning; Multiplexing; Noise levels; Optical and optoelectronic circuits; Optical modulation; Optical pumping; Optical receivers; Optical sensors; Pump lasers; Pumps; Stimulated emission; Switching; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Time division multiplexing; Transmission and modulation (techniques and equipments); Tuning
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2003.822677

We quantify both theoretically and experimentally the speed requirements for tuning or switching the wavelength of Raman pumps in time-division multiplexed (TDM) pumping schemes. Our results indicate that a periodic sweep-pattern has to be repeated at a rate above 10 kHz to achieve a temporal Raman gain variation of less than 1 dB at an average on/off Raman gain of 15 dB in 100 km of transmission fiber. At a 10-kHz rate, the sensitivity penalty of an optically preamplified receiver following the 100-km TDM Raman span was measured to be 0.5 dB. Expressed in terms of pump laser tuning requirements, this translates into a switching time of 100 ns, requiring a modulation bandwidth of /spl sim/10 MHz. When cascading multiple TDM Raman pumped transmission spans, we calculate that the worst-case temporal dB-gain variation scales linearly with the number of spans. At a repetition rate of 50 kHz and when cascading 10 spans, we predict an additional 1 dB of margin needs to be allocated in the system's power budget.