Page 357 - Optical Communications Essentials

Manufacturing Issues

Manufacturing Issues 347

Metal-coated end
≤ 50 mm

Normal fiber buffer coating Bare fiber

Metal coating
at midspan
≤ 50 mm
Figure 20.11. Two possible locations for creating a metal
coating on a fiber to allow hermetic sealing to device
packages.

soldering and hermetic sealing. A typical coating length ranges up to 50mm,
and the thickness is less than 2µm. Metallic coatings can be put on either single
fibers or ribbon fibers.
As shown in Fig. 20.11, the metal coating can be at any location on the fiber.
For metallic coatings on the end, the metal can go completely to the fiber end,
or a short final length of fiber can remain bare so that it may be terminated
with ceramic ferrules, fusion-spliced to another fiber, or connected directly to a
device inside a package. In the midspan metallization only a short section near
the end of the fiber is metallized. When such a fiber passes through a package,
it can be soldered to the package at the midspan point, thereby leaving a short
pigtail within the package for connecting to a device inside.

20.5. Emerging Package Technology
Although most devices for optical fiber communications are enclosed in her-
metically sealed metallic packages, there is a trend to produce both hermetic
and non-hermetic ceramic packages. This development is being driven by the
need to reduce manufacturing costs and to produce packaged devices in very
high volumes. The mechanical structure that houses active components usually
is the industry-standard hermetically sealed 14-pin butterfly package or some
variation thereof.

20.6. Summary
The successful application of any emerging technology lies in the implementa-
tion of cost-efficient component production. This is especially challenging in
optical communications where new concepts have been appearing rapidly and
standards are not fully mature in many areas. Ways of achieving this include
adapting semiconductor manufacturing techniques, setting up automation
processes, and devising reliable optoelectronic packaging methods.

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