Abstract

Erbium-doped fiber amplifiers (EDFAs) and tunable fiber Fabry-Perot (FFP) filters have been used recently in robust direct detection receivers.^1,2 These receivers use commercially available fiber-based components and achieve nearly the same sensitivity and selectivity as coherent systems with far less complexity and expense. In addition the FFPs are wavelength-locked³ preventing signal loss from wavelength drift of the source or receiver. The 40-nm (>5000-GHz) spectrum of EDFAs will support 1000 channels of dense wavelength-division multiplex (WDM) signals; however, FFP filters with finesses of 2000 will be required.⁴ The necessary finesse was recently reported in a two-stage FFP filter;⁵ however, wavelength was scaled by a factor of 10 to 400 nm and both stages of the filter were not wavelength-locked simultaneously.

© 1992 Optical Society of America