Theoretical and experimental demonstration of phase locking technology by utilizing cubic susceptibility medium

Abstract

ABSTRACT A novel proposal for phase locking based on cubic susceptibility medium has been theoretically proposed and experimentally demonstrated. The expression for phase difference between injected waves is yielded from the coupled wave equations, which implies the phase noise can be eliminated through low-efficiency four-wave mixing (FWM). Beat-note signal and autocorrel ation trace heterodyned by the in jected waves with small and large detune are adopted to assess phase locking effect, and they are monitored by electrical spectrum analyzer (ESA) and autocorrelator (AC) respectively. Moreover, the influence of polarization state on pha se locking is also investigated, and experimental results match well with the theoretical predictions. Keywords : phase locking; four-wave mixing; electrical spectrum an alyzer; autocorrelation trace; 1. INTRODUCTION With the development of radio-over-fiber (RoF) distribution technology [1], numerous of new methods for phase locking have been introduced. In future cellular radio networks, RoF is a very attractive technology for imparting microwave and mm-wave signals that contain broadband multimedia services to numerous base stations (BSs) of a network [2,3]. Numerous methods for the generation of microwave have been introduced in recent years. In 2009, Yao et al have utilized the wavelength-switchable single-longitudinal mode dual-wavelength erbium-doped fiber laser to generate switchable microwave [4]. Yao et al have also proposed a scheme for generating frequency-switchable microwave byLQFRUSRUDWLQJDKLJKILQHVVHULQJILOWHULQWRDGXDOZDYHOHQJWKV LQJOHORQJLWXGLQDOPRGHILEHUODVHU>@7KHSRWHQWLDOFKDOOHQJHIRUREWDLQLQJWKHVWDEOHPLFURZDYHVLJQ DOVIRFXVHVRQWZRNH\GLIILFXOWLHV  WKHVLQJOHORQJLWXGLQDO PRGH 6/0 ODVHU LV DQ HVVHQWLDO FDQGLGDWH IRU VXSSUHVVLQJ WKH PLFURZDYHV FDUU\LQJ WKHIUHTXHQFLHVRWKHUWKDQWKHGHVLUHGIUHTXHQF\ WKHRSWLFDOSKDVHORFNLQJ 23/ ZLOOEHDQRWKHUNH\WHFKQLTXHWKDWHQVXUHVWKHVWDEOHPLFURZDYHVLJQDOV In view of this, a new configuration for locking the phase of two uncorrelated waves that stimulated from different tunable lasers (TLs) is constructed. Thanks to the self-modulation and cross-modulation effects that exist in the cubic susceptibility medium, we utilize the highly nonlinear fiber (HNLF) as the potential candidate which plays a role as a “phase fixer”, the comparison results of adding and not adding the HNLF