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How to attach the fiber cable to the laser beam coupler
Only use fiber cables terminated with FC-APC (8° angle) connectors as provided by Oxxius. To attach such a
fiber:
- Make sure that the pin screw holding the connector ferrule is loosened and does not impair the
movement of the ferrule into its holder (see Figure 4-3). Failing to do so might damage the
connector;
- Approach the fiber connector at an angle (as shown on Figure 4-3) and insert the ferrule into the
beam coupler, carefully avoiding any contact on the ferrule’s end face;
- Once the ferrule is inserted, align the connector’s key with the notch on the coupler, then gently
push the connector inside the coupler and lock the connector’s box nut by rotating it to the right (do
not use any tools to fasten the connector);
- Fasten the coupling nut of the connector completely;
- Slightly and gently fasten the pin screw in order to reduce the slackness of the ferrule inside the
alignment sleeve. Be warned that fastening the screw too hard can affect the polarization state in
the fiber and damage the screw.
Figure 5-3: Pin screw (coupler side) and connector’s key
Finding a signal
To inject a laser beam into a fiber, one has to align the focus point of the coupling lens with the center of
the fiber’s core. Given the core size of a single-mode fiber (typically a few microns), the alignment
procedure is painstaking and requires both patience and precision in the handling of the coupler.
You will need an optical power meter equipped to accept your fiber’s connector and able to measure optical
powers ranging from a few tens of µW to a few tens of mW.
Firstly, make sure that the three counter screws (see Figure 4-4) are loosened by 2 or 3 full turns.
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