One of the key technology enablers for the future all-optical networks, particularly ones with ultra-long-haul, burst- or packet-switching capabilities, is the all-optical signal processing including signal regeneration, wavelength conversion, and switching. While many different all-optical implementations of these functions have been proposed over the last two decades, they all face one major challenge: in order to become viable alternatives to their electronic counterparts, the all-optical signal processors need to realize the full advantage of inherent parallelism of optical processing. This means they must be able to handle simultaneously many optical channels carried by different wavelengths (i.e. support wavelength-division multiplexing, or WDM) without dramatic increase in complexity and cost. Until recently, this challenge has seemed to be insurmountable. Indeed, an all-optical signal processor fundamentally relies on strong nonlinear-optical effects, which in turn lead to debilitating interaction among the WDM channels, e.g. by means of four-wave mixing (FWM) and cross-phase modulation (XPM). So far, attempts to perform nonlinear-optical processing of multiple WDM channels have proved unsuccessful.
In collaboration with group of Prof. T. I. Lakoba (University of Vermont), we have proposed a way solve this problem and enable simultaneous nonlinear-optical signal processing of many WDM channels (see references [1,2] below). The essential feature of our approach is using a novel nonlinear-optical medium with peculiar dispersion properties. These properties are such that different frequency components within each WDM signal’s spectrum propagate with nearly the same velocities to support integrity of the pulses and strong intra-channel nonlinearity. At the same time, velocities of any two separate WDM channels are considerably different, ensuring mitigation of inter-channel nonlinear effects through significant FWM phase mismatch and fast XPM bit walk-off between the neighboring channels. The nonlinear material with such dispersion properties does not exist in nature, but can be constructed artificially by alternating sections of highly-dispersive Kerr medium (e.g. optical fiber) and optical filters with periodic group delay response (periodic group-delay devices, or PGDDs).
After some preliminary work reported in [3,4], we have experimentally demonstrated multichannel all-optical signal processing based on this principle in [5]. We are currently working on extending this method to more complicated modulation formats, such as DPSK and DQPSK [6,7].
Selected publications
- M. Vasilyev and T. I. Lakoba, “All-optical multichannel 2R regeneration in a fiber-based device,” Opt. Lett. 30, 1458–1460 (2005).
- T. I. Lakoba and M. Vasilyev, “A new robust regime for a dispersion-managed multichannel 2R regenerator,” Opt. Express 15, 10061–10074 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-16-10061 .
- P. G. Patki, V. Stelmakh, M. Annamalai, T. I. Lakoba, and M. Vasilyev, “Single-Channel 2R Regeneration in Quasi-Continuous Dispersion-Managed Nonlinear Medium,” Frontiers in Optics / Laser Science XXIII Meeting, September 2007, San Jose, CA, paper FThS3. Best Student Presentation Award.
- P. G. Patki, M. Vasilyev, and T. I. Lakoba, “All-optical regeneration of multi-wavelength signals,” the IEEE LEOS European Winter Topical on Nonlinear Processing in Optical Fibres, Innsbruck, Austria, January 12–14, 2009, paper WC2.3.
- L. Li, P. G. Patki, Y. B. Kwon, V. Stelmakh, B. D. Campbell, M. Annamalai, T. I. Lakoba, and M. Vasilyev, “All-optical regenerator of multi-channel signals,” Nature Comm. 8, 884 (2017).
- T. I. Lakoba, J. R. Williams, and M. Vasilyev, “NALM-based, phase-preserving 2R regenerator of high-duty-cycle pulses,” Opt. Express 19, 23017–23028 (2011), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-23-23017 .
- T. I. Lakoba, J. R. Williams, and M. Vasilyev, “Low-Power, Phase-Preserving 2R Amplitude Regenerator,” Opt. Commun. 285, 331–337 (2012).