S band gain-clamped erbium-doped fiber amplifier by using optical feedback method

We have proposed and experimentally demonstrated an S band gain-clamped erbium-doped fiber amplifier, which provides an operation range from 1480 to 1520 nm by using an optical feedback method. The behavior and performance of gain clamping in S band have also been investigated experimentally under different operation conditions.

I. Introduction

Wide-Band erbium-doped fiber amplifiers (EDFAs) have been intensively studied for wavelength-division-multiplexing (WDM) systems. The stabilized gain versus the variation of input signal power is one of the key issues for WDM networks. Several gain-clamping techniques have been reported, such as the all-optical gain-clamped method [1], or different optical filters including fiber Bragg grating filters, finer acoustooptic filters, and tunable bandpass filters (TBFs) [2]– [4], covering both and bands (1530–1610 nm). In addition, the gain-clamping effect by using an optical feedback has been shown [1], [3], [4]. Recently, an band (1450–1530 nm) amplification technique, which employs the erbium-doped silica fiber with depressed cladding design and 980-nm pump laser to generate EDF gain extension effect, has been reported [5]. Therefore, the gain clamping technique is expected to extend to band by using this band amplifier module. In this letter, we present a gain-clamped band amplifier with a forward optical feedback configuration over the operation range from 1480 to 1520 nm. The gain clamping behaviors have also been investigated experimentally. Fig. 1.

Experimental setup of band EDFA module with forward optical feedback for gain clamping.