Schäfter+Kirchhoff 60FC-A19.5 Series User manual

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
1
Fiber Couplers Series 60FC-A19.5
The Schäfter+Kirchhoff fiber couplers series 60FC-A19.5 collimate the radiation from a polarization-maintaining
single-mode fiber or from a multi-mode fiber.
This document provides assistance in installing and adjusting the fiber couplers series 60FC-A19.5. It
describes, how a fiber cable is attached and how the collimation setting is adjusted. Additionally it describes
how the series 60FC-A19.5 fiber couplers reversely are used as an in-coupler for multi-mode fiber cables.
1. Before You Start
The fiber coupler is shipped with a protection cap for the fiber receptacle and with a front cap.
Please remove all the protection caps first and do not use them as beam
dumps (risk of photo contamination).
Notice:
There is a two-part protection cap on the receptacle. Please perform the following steps in order to remove
this cap:
Figure 1:
First, remove the threaded cap from
the fiber receptacle of the fiber
coupler.
Figure 2:
Then, slightly loosen the small pin
screw. Use the screwdriver 9D-12.
Make sure to not loosen it too far, as it
is small and easily lost.

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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Figure 3:
Now, pull out the plug.
Now, make sure that the connector of the fiber you want to attach matches the receptacle type of the fiber
coupler:
• Use fibers with FC-APC (8°-polish) connectors for fiber couplers with an inclined coupling axis
(60FC-A19.5-4).
• Use fibers with FC-PC (0°-polish) connectors for fiber couplers with a coaxial axis
(60FC-A19.5-0).
The fiber couplers are compatible to all fiber connectors type FC, including fiber connectors with end caps
(single-mode only).
• Do not touch either the optical surface of the lens or the fiber end-face.
• If the coupler is not in use, reattach both rear and front protection caps.
Notice:
Refer to the laser instruction manual for all instructions regarding laser
safety!
• Do not stare directly into the laser beam (which can cause permanent
damage to the eyes).
• Do not stare at the reflected beam from reflective objects.
• Do not point the laser beam to other individuals.
Caution!

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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2. Attaching a Fiber Cable to the Fiber Coupler
For attaching a fiber cable to the fiber coupler perform the following steps:
Figure 4:
To prevent damage to the sensitive
fiber end-face, always insert the fiber
connector`s ferrule Aat an angle, with
the connector key Bproperly aligned
to the receptacle notch C.
Figure 5:
When the ferrule tip is safely located
in the inner cylinder of the receptacle,
align the connector to the
receptacle axis and carefully introduce
the connector into the fiber coupler.
Figure 6:
Then, orient the connector key in a
way that it is pressed gently onto
the right-hand side of the receptacle
notch.
Figure 7:
Gently screw on the connector cap
nut onto the receptacle until it is
finger-tight.
A
B
C

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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Figure 8:
Finally, gently tighten the fiber grub
screw to reduce the free play of the
ferrule in the receptacle.
The free play in between the connector ferrule and receptacle is only a few microns, but necessary for
inserting the ferrule without force.
The tightened grub screw and the right-hand orientation rule for the connector, ensure a high reproducibility
in mode field position and angle, which is especially important for attaching and reattaching polarization-
maintaining fibers reproducibly.
3. Adjusting the Focus Setting
Focus adjustment (adjustment of the coupling lens in z-direction) is a demanding task and should be
performed preferably using a collimating telescope.
The fiber coupler is shipped pre-adjusted for the labeled wavelength and,
often, it is not necessary for the customer to readjust the coupling lens
position. This is why you can skip this step in most cases.
Notice:
To check the collimation setting of the fiber coupler, couple a radiation source of appropriate wavelength into
the fiber connected to the fiber coupler.
Refer to the laser instruction manual for all instructions regarding laser
safety!
• Do not stare directly into the laser beam (which can cause permanent
damage to the eyes).
• Do not stare at the reflected beam from reflective objects.
• Do not point the laser beam to other individuals.
Caution!
Depending on the fiber type used with the fiber coupler there are two options:
• If you use the fiber coupler with a multi-mode fiber, use the factory setting. In case of
in-coupling high power levels into a multi-mode fiber, a fine-adjustment of a fiber coupler already
installed is described in Chapter 7.
• If you use the fiber coupler with a single-mode or polarization-maintaining fiber, you can use the
following procedure:
Direct the beam to a target about half a Rayleigh length zRaway:
zRπ∙∅2
beam
=
2 λ∙8

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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Here λ is the optical wavelength and Øbeam the collimated beam diameter (1/e2level).
When correctly collimated, the laser spot diameter on a target about zR/2 away must have
approximately the same diameter such as the beam directly behind the laser beam coupler.
Additionally, make sure that there is no focused spot between the laser beam coupler and the
target at zR/2.
The lens position is adjusted by means of an eccentric key. The eccentric key type 60EX-4 is used for fiber
couplers with focal lengths ≤11 mm. For fiber couplers with focal lengths ≥12 mm please use the eccentric
key type 60EX-5.
For adjusting the lens position perform the following steps:
Figure 9:
Loosen the two grub screws fixing the
lens position by means of a screwdriver
type 9D-12.
Figure 10:
Insert the eccentric key type 60EX-4 or
type 60EX-5 into the large hole.
Figure 11:
Now, adjust the focus setting by ro-
tating the eccentric key. Adjust the
collimation by minimizing the size of the
laser spot on the target about half the
Rayleigh length zRaway.

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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Figure 12:
Finally, fix the two grub screws in order
to lock the focus setting.
4. Adapter for the Lateral Adjustment
The fiber coupler can be connected to your laser system or optical bench by using an adapter flange or it can
be attached directly to a multicube element from Schäfter+Kirchhoff.
It is very important for an efficient coupling that the laser beam passes the aperture of the fiber coupler cent-
rally.
Many lasers, such as HeNe lasers or DPSS lasers, have a 1´´ x 1´´ drilling pattern around the beam exit. For the-
se lasers, Schäfter+Kirchhoff offers an adapter flange which can be moved laterally in oversized holes in order
to center the adapter flange to the laser beam (Figure 13). Always attach the flange with the recommended
washers and spring washers.
Figure 13:
DPSS laser with a 1´´ x 1´´ drilling
pattern and attached adapter type
60A19.5-F.
The proper centering of the beam can be tested by attaching an aperture type 13H or a variable iris diaphragm
type 13BL1-13 instead of the laser beam coupler (Figure 14).
For centering the adapter flange, perform the following steps:
Figure 14:
Instead of a 60FC-A19.5 fiber coupler,
an aperture 13H is attached.

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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Measure the power transmitted by this aperture. Maximize the transmitted power by laterally shifting the
adapter. The adjustment is most sensitive if the aperture diameter is chosen to be about 70% of the collimated
beam diameter (1/e2).
Figure 15:
Laterally shift the adapter in order to
maximize the radiation that is trans-
mitted by the aperture.
Only a coarse alignment is necessary, which can be done by hand (Figure 15), as the positioning accuracy
must only be a fraction of the collimated beam diameter.
Figure 16:
Finally, fix the adapter and remove the
aperture.
If you have performed the described steps in this chapter accurately, you can
skip the subsequent optimization of the fiber coupling described in chapter
6. The fiber-coupling efficiency should already be good.
Notice:

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
8
5. Connecting the Fiber Coupler to Your System
Before you install the fiber coupler we recommend to measure the output power of the laser as a
reference for the next steps.
Now, perform the following steps:
Figure 17:
Locate the three radially arranged
tapered pin screws in the adapter
flange and loosen them using the hex
screwdriver 50HD-15.
Figure 18:
Gently introduce the fiber
coupler into the vacant aperture. Make
sure that none of the tapered pin
screws are located in the gap.
The ∅19.5 mm system mount of the 60FC-A19.5 fiber coupler has a steel
ring. This steel ring has a gap of approx. 2 mm, see Figure 18. Please make
sure that none of the three pin screw is located in the gap of the steel ring.
Otherwise the connection in between the adapter and the fiber coupler and
therefore the alignment is not long-term stable.
Attention:
Figure 19:
Now, fix the three tapered pin screws
at the adapter flange. please use the
same torque of about 0.48 Nm for all
three pin screws, respectively.

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
9
6. Optimizing the Fiber Coupling
When coupling into multi-mode fibers, the fiber couplers should produce a small focus at the fiber end-face.
Thus, coupling a laser beam into a multi-mode fiber requires precise adjustment and needs some patience.
Refer to the laser instruction manual for all instructions regarding laser
safety!
• Do not stare directly into the laser beam (which can cause permanent
damage to the eyes).
• Do not stare at the reflected beam from reflective objects.
• Do not point the laser beam to other individuals.
Caution!
Measure the coupled light at the opposite end of the fiber cable using a light detector or power meter. The
detector may have to be adjusted to maximum sensitivity in order to detect a low transmission level possible at
beginnig of the following adjustment step:
Figure 20:
Slightly loosen the the four screws
fixing the flange.
Figure 21:
Laterally shift the adapter in order to
maximize the radiation that is
detected at the fiber end.
Figure 22:
Now, fix the four screws at the flange.

Fiber Couplers Series 60FC-A19.5
Adjustment_60FC-A195 18.05.2021 © Schäfter+Kirchhoff GmbH
Schäfter+Kirchhoff GmbH Kieler Str. 212 22525 Hamburg, Germany [phone] [email protected] www.sukhamburg.com
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7. Focus Setting in Case of High Power Levels
If you have performed the previous steps described in chapters 1-5 (+ 6 if necessary), the fiber coupling to the
mult-mode fiber is already optizimed.
However, if the laser has a high power level it might be advisable to readjust the focus setting in a further step.
With the default focus setting a small focus is produced exactly at the end-face of the fiber. Therefore the
power density is quite high, which can cause problems.
You can decrease the power density at the fiber end-face, by slightly de-adjusting the focus setting for
high power level lasers. If done right, the fiber coupling efficiency will still be high, but power density will be
decreased.
A fine-adjustment of the focus setting of the fiber coupler - if necessary - is performed in the following steps:
Figure 23:
Slightly loosen the lens by the loo-
sening the two grub screws. Use the
screwdriver type 9D-12.
Figure 24:
Use the eccentric key type 60EX-4 or
60EX-5 for fine-adjusting the focus
setting. Point the index Dinto the
direction of the fiber.
Turn the eccentric key slightly in both directions. There is a range in which the radiation coupled to the fiber
does not decrease. Adjust the focus setting to one edge of this range. Preferably, use the setting where the
index of the eccentric key points into the direction of the fiber.
Figure 25:
Finally, lock the focus setting by
fixing the two grub screws using the
screwdriver type 9D-12.
D