Wavelength-tunable add/drop multiplexer for dense wavelength division multiplexing using long-period gratings and fiber stretchers

We have designed and configured a novel wavelength-tunable add/drop multiplexer (ADM) device that employs long-period gratings (LPGs) and piezoelectric ceramic fiber stretchers. The modeling for this ADM predicts that 50 International Telecommunication Union (ITU) dense wavelength division multiplexing (DWDM) channel signals could 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 erbium-doped fiber amplifiers. The cross-talk between channels is less then -39 dB, and the total insertion loss of the device is about 0.24 dB which includes the splicing losses, the mode mismatching loss, and the expected losses in the two side-by-side coupled fibers. The tuning of add/drop channels within a limited region can be provided by changing the voltage, which is applied to the piezoelectric ceramic fiber stretchers. This technique is suitable for the in-line implementation of optical communication networks.