INTERNATIONAL JOURNAL OF MICROWAVE AND OPTICAL TECHNOLOGY VOL. 1, NO. 2, AUGUST 2006 IJMOT-2006-6-99 © ISRAMT 2006 Optical Performance Monitoring in DWDM Networks Using Channel's 2 nd Harmonic Generation Moncef B.Tayahi * , Sivakumar Lanka, and Banmali Rawat Advanced Photonics Research lab, Department of Electrical Engineering University of Nevada, Reno, NV 89557, U.S.A. Tel: 1-775-784-6103; Fax: 1-775-784-6627; E-mail: moncef@engr.unr.edu Abstract- Optical second harmonic generation in dense wavelength division multiplexing was used to monitor the performance of each channel in all dense wavelength division multiplexing (DWDM) optical networks using a highly nonlinear photonic crystal fiber. Index Terms- Fiber measurements, Networks, Holey Fiber I. INTRODUCTION Present optical communication systems require optical-electronic-optical (O-E-O) for nearly all operations in the network which is not only expensive, but also restrictive; it prevents optical transparency, discards many of the attributes of optical signals, such as phase, frequency, polarization, and prohibits the use of advantages of optics, such as ultra fast processes on picoseconds and sub-picoseconds time scales. Our approach aims at making compact, efficient and functional subsystems that can perform as many functions as possible such as real time monitoring of complex all optical DWDM networks [1-2]. Our prior work used poled Lithium Niobate (PP-LNO 3 ) for the second harmonic generation, however, it was shown that SHG conversion efficiency was low and new photonics bandgap fibers provide better conversion efficiency [3]. Optical signal to noise ratio (OSNR) is an important analog performance parameter that is often considered for monitoring optical networks [4]. Optical filtering in optical add-drop multiplexers (OADM’s) and optical cross- connects (OXC’s) reshape the noise background. Interpolation of the noise background across the band can also be excluded by optical switching because each channel can acquire a unique noise background. The parameters that most OPMs measure directly are average optical power and wavelength; typically using a few percent of the signal power extracted from the transmission fiber. From these direct measurements, a host of critical network performance parameters can be derived, such as channel presence verification, channel wavelength, ASE noise, and optical- signal power, optical SNR (OSNR) per channel, optical-amplifier gain, and gain tilt, signal Q- factor where the BER can be estimated [5]. These parameters may then be used to manage network reliability and define a quality of service for end customers. II. NONLINEAR CONVERSION Our study explores novel techniques to find the best possible approach in order to develop integrated optical performance monitoring to realize transparency in optical networks. The specific device being used for second harmonic generation is a highly nonlinear photonic crystal “holey fiber” which can be used for super continuum generation. The relation between the fundamental power and the second harmonic power for a photonic crystal fiber is given by [6]: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = ∆βL 2 1 sinc ∆β A c ε n n P d 8w P 2 2 ovl 3 0 2 0 2 w 2w 2 w 2 eff 2 2w (1) where ‘w’ is the fundamental frequency, A ovl is 583