Abstract

Tunable laser sources are critical components for DWDM networks as spare sources or fast wavelength-switching devices. The wavelength monitor for controlling a tunable laser diode must cope with multiple output wavelengths and the required tuning speed. Fabry-Perot (FP) etalons have been commercially used for wavelength control of DWDM lasers. However, a FP etalon cannot distinguish among different channels since it has periodic wavelength characteristic. This makes it difficult to monitor the mode-hopping problem that might happen in tuning a tunable laser.¹ Etalons with special tuning mechanism or array waveguide gratings were also proposed to monitor tunable lasers,^2,3 but they may have limited response speed or require expensive components. On the other hand, wavelength monitoring by detecting the transparent current or the induced junction voltage across a FP laser diode (FPLD) was demonstrated to provide 0.01-nm wavelength resolution.⁴ This approach is very attractive since the wavelength sensor can be monolithically integrated with the tunable laser. Moreover, a FPLD can easily be tuned to monitor multiple channels by adjusting its bias current. However, to achieve 0.01-nm resolution with this approach requires tough stability on temperature control.

© 2002 Optical Society of America