Promising compact wavelength-tunable optical add-drop multiplexer in dense wavelength-division multiplexing systems.

We design and model a highly compact and tunable optical add-drop multiplexer (OADM) device that consists of long-period gratings and piezoelectric ceramic fiber stretchers. The proposed OADM shows that 50 dense wavelength-division multiplexing channel signals can be selected in the wavelength range from 1526.25 to 1563.75 nm with 0.75-nm channel spacing, which covers the whole C-band gain spectrum of an erbium-doped fiber amplifier. The cross talk between channels is less than -39 dB, and the total insertion loss of the device is approximately 0.24 dB, which includes the splicing losses, the mode mismatching loss, and the expected losses in the two side-by-side coupled fibers.