How the new Kovar hermetic packaging solution suppresses thermally induced insertion loss fluctuations to ±0.03dB

(Tokyo) When NGK Electronics' high-density FA connector (Fiber Array Connector) continued to work under 28Gbps PAM4 modulation, engineers observed strange signal jitters. Recently, the Optical Communication Technology Review published an experimental report pointing out that the micron-level deformation caused by the mismatch of the coefficient of thermal expansion (CTE) has become an invisible killer of high-end optical modules.

Pain point hit
NGK's official product page shows that the assembly tolerance of its MT ferrule and ceramic sleeve must be controlled at <0.5μm. However, in the vehicle temperature cycle from -40℃ to 85℃, the difference in thermal deformation between the traditional stainless steel housing and the ceramic substrate is as high as 4.7ppm/K, which directly leads to:

Fiber V-groove alignment deviation ➔ Insertion loss fluctuation exceeds the industry standard by 62%
Welding point cyclic stress fatigue ➔ Air tightness decays to 10⁻⁶ Pa·m³/s after 500 cycles

The fourth-order gradient sealed Kovar housing developed by our company for NGK-type high-precision optical devices:
CTE Magician - By adjusting the Fe/Ni/Co ratio, it can achieve super matching with zirconia ceramics at 0.05ppm/K (data see Fig.1)
Stress dissolution - Laser micro-melting welding replaces brazing, and the heat-affected zone is reduced to 15μm (traditional process>100μm)
Vehicle-grade armor - Passed the IEC 61373 vibration shock test, and the fiber offset is <0.2μm under 40G acceleration
Breakthrough in actual measurement

In cooperation with a top optical module manufacturer in Japan, the multi-channel Kovar tube shell using this solution:

✅ The plug-in life is increased to 1500 times (3 times beyond the GR-326-CORE standard)

✅ The helium leak rate in an 85% humidity environment is stable at 5×10⁻⁹ Pa·m³/s

This packaging structure reduces the optical coupling efficiency fluctuation of our 128-channel FA connector in temperature cycling to an unprecedented ±0.9%”