Application Analysis of Hermetic Packaging in Optical Communication

1. Hermetic Requirements of Optical Communication Modules

The laser chips and photodetector chips inside optical communication modules are extremely sensitive to moisture — moisture attacks the anti-reflection coating on the chip surface and causes output power to drop.

Industry requirements on internal moisture content are extremely strict:

The Telcordia GR-468 standard requires that the internal moisture content of an optical communication module be <5000 ppm (5000 parts per million). Meeting this figure requires two things: the package itself must be hermetic, and after assembly it must be backfilled with high-purity nitrogen before being sealed.

2. Typical Optical Communication Packaging Solutions

Two mainstream package formats:

TO-CAN packages — a cylindrical metal housing in which the laser or detector chip is mounted on the header and sealed on top by a lensed cap. GTMS solution: Kovar header + borosilicate glass insulator. Compact and low-cost, it suits short-reach optical modules and datacom lasers. The TO56-7PIN header and the TO9-2P2L-2.2K header shipped in volume by Xuri belong to this category; paired with optical windows and caps, they provide optical-module customers with a complete hermetic housing solution.

Butterfly packages — butterfly-shaped metal housings, such as Xuri’s BTF-30*12.7-S product. CTMS solution: ceramic substrate + Kovar housing, with pin counts of up to several dozen. Excellent heat dissipation and rich functionality make them suitable for long-reach high-speed optical modules and high-power pump lasers.

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[Glossary]

1. TO-CAN (Transistor Outline CAN): a cylindrical hermetic optoelectronic package derived from the transistor-outline standard; the most compact package format in optical communication

2. Butterfly Package: a rectangular hermetic optoelectronic package with wing leads that can integrate TEC and other temperature-control components; suitable for high-performance optical modules

3. ppm (Parts Per Million): one part per million, used to quantify internal moisture content; 5000 ppm ≈ 0.5% by volume