Raman assisted fiber wavelength conversion for high-speed optical processing in optical networks

Ultra-fast optical packet communications, with packet bit rates exceeding 160Gb/s, is a key next step in the evolution of ultra-high capacity optical networks. It is envisioned that in the next generation of networks, all-optical switches will be used to perform switching and routing functions in the optical domain. Optical signal processing technologies using various nonlinearities in fiber have the most potential of operating at these high bit-rates due to their femto-second response time. Conventionally fiber is treated only as the nonlinear interaction medium. This work presents a novel idea of using Stimulated Raman Scattering to turn the passive fiber into both gain medium and nonlinear interaction medium and hence enhance the processes. Mainly the assistance of distributed Raman gain on two important nonlinear effects, cross-phase-modulation (XPM) and four-wave-mixing (FWM) is investigated and demonstrated in optical systems with excellent performances. Wavelength conversion using Raman enhanced XPM is first demonstrated at both 40Gb/s and 80Gb/s using two different types of fibers. With 600mW of Raman pump power, total conversion efficiency of 21dB is achieved. Bit error rate (BER) measurement shows good system performance as well as the wavelength converter's regeneration properties. Then a 160Gb/s to 10Gb/s low sensitivity all optical demultiplexer (optical data rate converter) is developed using Raman enhanced FWM effect. A total demultiplexer efficiency enhancement of 19dB is measured with 400mW of Raman pump power. With the availability of the demultiplexer, two wavelength conversion techniques based on XPM and FWM are achieved with excellent performance at 160Gb/s. They are then compared with regard to system performance and functionalities. Both of these techniques have the potential to scale to even higher bit rates.; Finally an all-optical packet routing architecture, all optical label swapping (AOLS) is described and its implementation at record 160Gb/s data rates is demonstrated using the developed Raman enhanced fiber optical signal processors. It shows the transparency of AOLS technologies from previous demonstrated 2.5Gb/s to this record high 160Gb/s using a common routing and packet lookup framework. Packet forwarding/conversion, optical label erasure/re-write, and signal regeneration at 160Gb/s have been achieved using this technique.