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Wave Length Indicator
Wily was in his back yard trying to get
his beagle “Gizmo” to stop barking at a squirrel running along the fence when his cordless
phone rang.
The call was from a company, which
installed optical fiber communications systems. The caller described a simple
battery powered device they needed designed and built for them. The company
installed several types of optical fiber systems and needed a quick way to spot check to
see if a fiber cable was active with light and determine which one of 4 wavelengths was
being used.
Wily said he thought he could build such
a device. They agreed on a rough price for the work and Wily went to his basement
lab to get started on the project. Thus began the Optical Fiber Wavelength
Indicator project.
The first thing Wily had to do was find some suitable
light detectors. As the drawing below illustrates, silicon detectors only worked to
about 950n. The company wanted to detect an optical fiber carrying four different
wavelengths. They wanted to detect 850nm, 1300nm, 1550nm and 1625nm. Wily thought
that with a bit of calibration, a single type of Germanium photodiode would be able to
cover all the wavelengths. |
