Wavelength Division Multiplexers for 980 nm Pumping of Erbium-Doped Fiber Optical Amplifiers

The choice of wavelength division multiplexer (WDM) couplers for use in fiber-based optical amplifiers is extremely important to obtain optimum device performance. At a minimum, these devices need to have low insertion loss at the doped-fiber pump and signal wavelengths, λp and λs. Small splice losses between the coupler input pigtail and the incoming telecommunication fiber at λs and between the coupler output pigtail and the Er-doped gain fiber at λs and λp are important to maximize amplifier signal-to-noise and to efficiently use available pump power. In addition, in high-gain amplifier applications, coupler backscatter and crosstalk may also impact noise. Finally, as practical amplifiers tend towards smaller physical size, bend induced loss in the coupler pigtails also becomes an important factor.