Novel bidirectional optical subassembly with embedded filter, <inline-formula><math display="inline" overflow="scroll"><mrow><mn>45</mn><mtext>-degree</mtext></mrow></math></inline-formula> angle polished fiber cladding and etched fiber core

Abstract

Abstract. The optical wavelength-division-multiplex filter for bidirectional optical subassembly ͑BOSA͒ is embedded to the fiber core, which results in simplicity of the BOSA module. The fiber cladding is 45-deg angle polished to receive a downstream signal. The core is etched by a femtosecond laser to have a normal core facet and to transmit an upstream signal. The downstream signal, which is core mode, is coupled to the cladding mode by the long-period fiber grating and then detected by a photodiode by means of the total internal reflection effect at the 45-deg angle polished cladding facet. The measured transmitted and received coupling efficiencies are 27.3 and 43.8%, respectively.