Novel laser fusion processes of fabricating low-loss S-band WDM narrowband coupler devices overcome H2O resonant absorption

In this paper, we have demonstrated low loss, narrowband and broad FSR WDM couplers made by laser fusion processes to overcome the water absorption loss. Insertion loss as low as 0.5 dB was measured at 1380 nm resonant wavelength for SMF-28 fiber. Preliminary analyses indicate insertion loss as low as 0.1-0.2 dB is very feasible and will be presented at the conference. Methodology and results for very high pump power testing are discussed. These all-fiber fused couplers capable of handling 11 watts of pump power and 2000 hours of high temperature and high power were demonstrated. Combing the low loss, high power, broad FSR, narrowband channel spacing, and high reliability, laser fusion WDM couplers can meet the most stringent optical amplifier applications.