Manufacturing approach simplifies high-interconnect optical subsystems production

The fiber optic switching component business is accustomed to expensive manufacturing facilities requiring the large workforce needed to align countless fiber optic strands. But this is not the only manufacturing approach that works today. Engineers at Network Photonics have developed a product design and manufacturing process that reduces facility and capital expenditures and results in decreased product costs.

The company's CrossWave all-optical wavelength switching subsystems are based on a one dimensional MEMS technology that allows for the switching of up to 96 wavelengths of light with just three ports per switch. By cascading CrossWave switches, multiple-port cross-connects can be assembled in a simple, cost effective manner. In order to manufacture the switches and ensure quality while minimizing product cost, an automated assembly and test process was developed by the company.

The process is based on a linear flow technology approach. The implementation of this methodology minimizes material movement and work-in-progress, while supporting the production of a variety of product configurations and ensuring total quality control throughout the various stages. In order to have a flexible and scalable process, the manufacturing line was divided into seven distinct operations each in a class 10 clean room environment. Establishing the tradeoffs for each station depends on the product design and results in a balanced process time for each station. This allows for individual stations to be added in order to expand capacity where production bottlenecks occur.

The custom tools and manufacturing processes for each of the automated stations are developed in-house in conjunction with the product design effort. This approach results in a development effort that optimizes the integration of the manufacturing process with the product design. Throughout the design process, constant exchanges were made between part design, manufacturing process and tool design. Cost, quality and performance implications are factored into these exchanges to arrive at an optimal solution for each step in the development process. To support the effort, individual roles and department missions were overlapped to ensure proper cross-functional communication within the organizational structure.

At the heart of the process are custom manufacturing tools used to produce the CrossWave optical switch. Although each manufacturing process has distinct operations to perform, the manufacturing of the CrossWave switch is based on micron and sub-micron alignment of precision optical materials. To best support these efforts, a common foundation in component usage, station design and software was developed for each of the tool sets. The tool sets have also been developed into one integrated design effort which further contributes to the common tool foundation goal.

Initially, common station footprints were established for the manufacturing line to allow for process flows to be changed and stations to be moved without running into line configuration issues due to a mismatch of station sizes — a critical consideration in a clean room environment. Once a common footprint was in place, a common set of precision motion stages were identified to support the micron and sub-micron alignments. Along with the selection of these precision alignment stages, the required vision systems cameras, illumination sources and lenses for the alignments were also established. The result is an assortment of common camera and lens combinations from one or two select suppliers. In addition, a common set of instrumentation such as control computers, swept tunable lasers/optical power detectors, polarization scramblers, and PDL meters were established for taking the precision measurements at each station.

The design effort for the manufacturing stations meant that all stations could take advantage of the common building blocks to establish a uniform platform for each subsequent operation. Each station has its own unique mechanical configuration to support the specific requirements of the process. While the stations may look mechanically different, all the underlying foundations are the same. As a result, tool design time and station costs are lowered and the repair and maintenance processes for the stations are simplified.

In order to integrate the manufacturing equipment, a common commercially available software platform was chosen to control each of the manufacturing tools. Resisting a common temptation to build an in-house test and control platform, we chose a flexible yet powerful platform that allows complete control of all aspects of the tool's process. The software was selected in conjunction with the key hardware components to ensure proper compatibility between all elements. As a result, individuals are hired with existing skills in place, the amount of unique software drivers for specific components types is minimized and out-of-house contractors can be brought in to support specific development efforts on an as-needed basis. All of these factors result in quicker development of the manufacturing tools and processes in conjunction with a fully integrated solution.

After the common platform was established for all manufacturing processes, the concept was extended to create a common test set for performing the qualification and final manufacturing tests on the CrossWave switch. Using many of the same instrumentation sets as the manufacturing tools, as well as the same software platform, the common test set provides all the control and measurement capability required by the engineering, quality, reliability and manufacturing organizations for product testing. This results in common test approaches, similar data reporting and proper correlation of results between equipment and organizations.

Breaking down the assembly and test of complex optical components into discrete manufacturing steps, and applying common assembly and test methodologies to the equipment and process design results in a repeatable, cost-effective and scalable manufacturing process. Of course, the key to achieving these types of results lies in the product design itself. An integrated product design that takes into account manufacturability is the formula to developing winning products.