PAWS~(TM) locker - A passively aligned internal wavelength locker for telecommunications lasers

摘要

This paper presents the passively aligned Wavesetter~(TM) (PAWS~(TM)) locker: a micro-optic subassembly for use as an internal wavelength locker. As the wavelength spacing in dense wavelength division multiplexing (WDM) decreases, the performance demands placed upon source lasers increase. The required wavelength stability has led to the use of external wavelength lockers utilizing air-spaced, thermally stabilized etalons. However, package constraints are forcing the integration of the wavelength locker directly into the laser module. These etalons require active tuning be done during installation of the wavelength locker as well as active temperature control (air-spaced etalons are typically too large for laser packages). A unique locking technique will be introduced that does not require an active alignment or active temperature compensation. Using the principles of phase shifting interferometry, a locking signal is derived without the inherent inflection points present in the signal of an etalon. The theoretical background of PAWS? locker will be discussed as well as practical considerations for its implementation. Empirical results will be presented including wavelength accuracy, alignment sensitivity and thermal performance.