Crosstalk, noise, and stability analysis of DWDM channels generated by injection locking techniques

Abstract

In this paper, theory and experimental results for wavelength-division-multiplexing (WDM) channel generation, formed by multi-line optical injection locking, is presented. A small-signal model to deal with wide-spectral-band optical injection problems has been developed. Based on this model, the crosstalk noise of an injection-locked laser in a coherent WDM system is assessed analytically. Experimental results on locking range, stability, and crosstalk noise confirms the modeling results, which indicate that stable and low-noise channels can be generated by this approach. Index Terms-Optical injection locking, optical transmitters, wavelength-division multiplexing (WDM). I. INTRODUCTION M OST current commercial dense wavelength-division multiplex (DWDM) systems operate with 2.5-or 10-Gb/s channel capacity. Due to a number of optical fiber and optical device impairments, the narrowest channel spacing used is currently 50 GHz. These figures lead to commercial spectral efficiencies limited to 0.2 b/s/Hz. One option to increase spectral efficiency is to increase the individual channel capacity to 40 Gb/s. The technology involves utilization of high-complexity components, with technological and physical impairments regarding group velocity and polarization mode dispersion in fiber, leading to limitations on the achievable transmission distance [1]. Another option is to reduce channel spacing. Apart from nonlinear interactions between the modulated optical carriers and the fiber-optic transmission medium, limitations here arise also from DWDM components. When reducing channel spacing to 25 GHz or less in a 10-Gb/s system, strict tolerances for center wavelength drift of components and lasers over operating temperature, aging, and measurement uncertainties apply.

Performance evaluation of CDMA, WDMA, DWDMA networks

“…One technique to overcome the above mentioned difficulties is to use the coherent channel forming scheme [11]. A novel architecture has been proposed which uses single frequency with small signal approach to estimate noise and crosstalk [12].…”

Theory and experiment of MEMS tunable lasers

“…In have been successfully demonstrated [34,35] but the theoretical analysis is not available since the previous small signal models (SSMs) in literature [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] are mostly for simple conditions such as weak injection power, single injection and single mode slave.…”

“…x is the grating pitch, m is the diffraction order, 6fo is the incidence angle, and Lang's theory has been extensively used and proven in many theoretical and experimental studies [63][64][65][66][69][70][71]. However, the small signal approximation and the combination of the effect of all the side modes into one mode would limit its validity in many cases such as large signal and strong side modes.…”

“…Horer and Patzak presented a large-signal analysis for wavelength conversion using two injection lasers simultaneously [63]. Cai et al proposed the generation of DWDM channels using multi-line optical injection and studied the associated crosstalk, noise and stability [64]. Alloptical regenerators and optical transmitters were also investigated using two side-mode locking method [65,66].…”

“…Especially the small signal analysis presented by Lang in 1982 [61] and later extended by Li using simple mathematics [109]. Their model has been extensively used and proven in many theoretical and experimental studies [63][64][65][66][69][70][71].…”