An in-depth introduction of FAU and its production
An in-depth introduction of FAU and its production
In the optical communication industry, FAU is a term that is often mentioned but seldom explained in detail.
FAU,short term of Fiber Array Unit. Simply put, it involves neatly arranging multiple optical fibers at fixed intervals and angles on a V-shaped groove substrate, pressing them down with a cover plate, and securing them with glue to form a standardized optical interface.
Sounds simple, right? But it's this seemingly simple part that is holding up the entire CPO industry chain. In actual structure, CPO relocates the optical engine next to the switch chip, achieving an order of magnitude higher precision in optical connectivity compared to traditional pluggable optical modules. And the core carrier of this precision is the FAU.
Let's examine FAU from every aspect: structure, technology, equipment, and the new requirements in the CPO era. After reading you will understand why a fiber array can hold CPO back.
V-groove substrate.
This is the soul of FAU, typically made of synthetic fused silica (Synthetic Fused Silica) or single crystal silicon (Single Crystal Silicon). The substrate surface is processed through optical etching or CNC precision machining to create a row of V-shaped grooves for positioning optical fibers. The precision of the spacing, angle, and depth of the V-grooves directly determines the performance ceiling of FAU.
Optical fibers.
Typically, SMF-28e single-mode optical fibers (1310nm/1550nm) are used. The coating on the ends of the optical fibers is removed to expose the bare fibers, which are then placed in the V-grooves in a one-to-one correspondence.
Cover plate.
It is pressed above the optical fiber to secure it in the V-groove and prevent it from shifting. The material of the cover plate is usually the same as that of the substrate (quartz or silicon).
UV epoxy Adhesive.
UV epoxy is used to bond the optical fiber, cover plate, and substrate together. The UV adhesive is initially cured, and then undergoes thermal aging (85°C/24h) for final curing, ensuring long-term stability.
Housing and connector.
The housing is made of SUS304 stainless steel and equipped with LC/SC/MPO connectors, forming a complete pluggable optical component. High-end FAUs are also sealed with nitrogen, with a gas tightness requirement of <1×10⁻⁸ atm·cc/s.
Obviously, FAU is not a small component; it represents the precision manufacturing threshold for CPO. It has evolved from a standardized passive component into a customized high-precision assembly. Whoever can achieve mass production on 64CH/128CH, 127μm/64μm pitch, and <0.3mm ultra-thin substrates will win the FAU market in the CPO era.
