Finally, gently tighten the fiber holding screw to reduce the slackness of the ferrule in the receptacle
as shown in Fig. 1, right. The inner cylinder has to be larger than the ferrule, to avoid jamming.
The holding screw together with the right-hand rule for the connector ensure a high reproducibility in
mode field position and angle, the latter being important for polarization maintaining fibers.
Collimating the Laser Beam
Focus adjustment (adjustment of the coupling lens in z-direction) is da demanding task and should
be preferably performed by use of a collimating telescope.
The collimator is shipped pre-adjusted for the given wavelength and, often, it is not necessary for
the customer to readjust the coupling lens position.
To check the focus setting of the fiber collimator, couple a radiation source of appropriate
wavelength into the fiber connected to the fiber collimator and direct the beam at a target about half
the Rayleigh length
z
R
away:
=
∙
Ø
∙
Here
λ
is the optical wavelength and
Ø
the collimated beam diameter (1/e
2
level).
Follow laser safety precautions!
When correctly focused, the laser spot diameter on a target about
z /2
away must have the same
diameter such as the beam directly behind the fiber collimator. Please make sure that the beam at
midpoint between the collimator and the target has the same diameter.
To adjust the focus, first loosen the two radially arranged pin screws that lock the coupling lens in
place, using screwdriver 9D-12 (Fig. 2, left).
The focus is adjusted by gently rotating the knurled ring. Adjust the focus by minimizing the size of
the laser spot on the target about half the Rayleigh length
z
R
away (Fig. 2, right).
After focus adjustment, relock the coupling lens into position by re-tightening the two radially
arranged pin screws.
Figure 2 left: Fasten/unfasten the pin screws
Figure 2 right: Slightly rotate eccentric key
pin screws (2x)
Schäfter+Kirchhoff
GmbH
OPTICS, METROLOGY, AND PHOTONICS
Schäfter + Kirchhoff GmbH
Kieler Str. 212, D−22525 Hamburg · Tel: (+49) 40 − 85 39 97 − 0 · Fax: (+49) 40 − 85 39 97 − 79 · e−mail: [email protected] · Web: http://www.SuKHamburg.de
