GAIN EQIALIZATION OF EDFA USING LEAKY STRUCTURES

Abstract

Erbium-doped fiber amplifier (EDFA) exhibits a non flat gain spectrum in the wavelength rage of 1470-1650 nm. An optical amplifier with flat gain spectrum is desirable to increase the capacity of current wavelength division multiplexed (WDM) and coarse wavelength division multiplexed (CWDM) systems. To utilize the whole spectral band of EDFA, continuous efforts have been made by various approaches (Embedded long period fiber grating filter, Phase shift long period grating, Arc and mechanically induced long period grating and leaky fibers). Recently tunable leakage loss behaviors of leaky fibers (Segmented cladding fiber, W-type fiber and Dual-core leaky fiber) have been utilized to demonstrate inherent gain flattening in newer band region (S-band —1470-1525 nm, L-band — 1565-1620 nm). In the present work we have used the dual core leaky fiber (DCLF) as an optical filter for gain equalization in C-band (1525-1555 nm). Fibre is characterized by two co-axial core and outer leaky cladding. A suitable design parameter can enable the coupling of power from inner core to high leaky outer core. Such a resonant fiber design show a spectral loss curve which resembles with the gain curve of the EDFA and has been used for gain flattening. We have studied the effect of various fiber design parameters on the performance of this optical filter. Our numerical results show that by using the suitable fiber parameters one can control the gain and the ripple upto desired level. We have presented a 30 dB flat gain in wavelength range of 1525-1555 nm with the ripple of ±1 dB by using the present optical fibre filter. The fiber can be fabricated by usual modified chemical vapour deposition technique (MCVD). Such optical filter can be useful in high data rate transmission system employing WDM.