Proceedings Article | 10 June 2004
KEYWORDS: Collimators, Tolerancing, Adhesives, Gold, Coarse wavelength division multiplexing, Process control, Packaging, Ultraviolet radiation, Free space optics, Mechanical engineering
In order to reduce size and cost, and at the same time increase overall performance, we designed a compact 8-ch CWDM MUX/DeMUX scheme based on free space optics. The device offers the following competitive performance specifications: IL < 0.8dB, IL ripple < 0.2dB, PDL < 0.1dB, PMD < 0.15ps, CD < 3ps/nm, IL uniformity < 0.3dB, adjacent channel isolation > 40dB, return loss > 50dB and pass-band bandwidth > 14nm. Such a device can operate in the temperature range of -10C° to 70C° with a TDL ~0.002dB/C°. In this paper, we will discuss the following three critical aspects of its design and implementation: (I) Design considerations and tolerance simulation. Here we discuss optimization of a set of critical design parameters: angle of incidence (AOI), beam size (BS), working distance (WD), filter aperture, filter orientation and filter-to-filter distance. (II) Build-in tolerance and critical alignment control. We have done extensive simulations to identify the critical variables and tolerance range for each variable. Based on this analysis, we then built in the alignment guidance and tolerances control into mechanical design. (III) Process control, material selection and surface preparation: Here we discuss the proper usage of the adhesives including the types of dual-effect adhesives, use of silica filler and coupling agent, surface preparation to achieve proper surface energy, tension and porosity, the optimum combination of the substrate and adhesive material for best shear and peel strength, and balancing temperature compensation and stress absorption.
