Fiber gratings based optical add/drop multiplexer with low interferometric crosstalk

Optical add/drop multiplexer (OADM) is one of the key components for WDM systems to enable greater connectivity and flexibility of the network. Fiber grating based devices seem to be promising candidates for OADMs. Two types of OADMs based on fiber gratings and circulators are demonstrated. A novel structure with cascaded gratings is proposed to reduce the interferometric crosstalk which severely degrades the system performance in the common structure. The add/drop multiplexing experiments of 4-channel WDM signals indicate that in the cascaded gratings structure there is 8 dB reduction of the crosstalk for the added signal compared with the common structure and a complete suppression of the crosstalk for the dropped signal