Cailabs Tilba R User manual

MITIGATE TURBULENCE
WITHOUT ADAPTIVE
OPTICS
INSTRUCTION MANUAL
2020/11

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TABLE OF CONTENTS
Introduction
Safety
Technical support
Warranty
Getting started
List of components
Unpacking
Product overview
Description
Operation instructions
Speciications
Mechanical drawing
Free Space alignment
Back-to-back in a single MUX/DEMUX coniguration
Back-to-back measurement with a MUX and DEMUX coniguration
Crosstalk and coupling eiciency calculation
Calculation of coupling eiciency
Calculation of crosstalk
Cleaning and maintenance
Cleaning instructions
Troubleshooting
1.
2.
3.
4
5
6.

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1. Introduction
TILBA-R is a Multi-Plane Light-Conversion (MPLC) based
spatial demultiplexer that decomposes a beam wave-front
proile into a limited number of spatial modes. The simultaneous
conversion of the spatial modes from the multimode input
(free space or ibered) into Gaussian modes of the SMF output
is eiciently performed using MPLC technology with high
power coupling and high mode selectivity.
The “Getting started” section below provides an overview of
the contents of the TILBA-R package as well as instructions
on how to set up the TILBA-R device. The following section,
“Product overview,” contains information about the product,
operating instructions and technical speciications. The
inal section, “Cleaning and maintenance”, addresses
troubleshooting and user maintenance.
Safety
Warning: The optical emissions from the optical
connectors and the optical iber are laser-based and may
be hazardous to your eyes. Please follow all the necessary
safety precautions.
Warning: All statements regarding technical data in this
instruction manual are only applicable when the unit is
operated correctly, according to its intended use.
Do NOT attempt to disassemble the TILBA-R. The device is
interdependent of its housing and therefore should never
be removed from it. Disassembling the TILBA-R voids the
warranty.
Handle the TILBA-R case with care.
Avoid impact or shaking the TILBA-R.
Do not pull or draw the ibers at the input and output ports of
the TILBA-R.
Do not unscrew the housing of the TILBA-R
Technical support
Warranty
Should you encounter any issues after reading this manual or
while using the TILBA-R spatial demultiplexer, please contact
Cailabs’ technical support:
Email: [email protected]
Phone: [phone]
Website: www.cailabs.com
Cailabs’ products are warranted to be free from defects as stated in Article 10, “Warranty”, of the General Terms and
Conditions, valid at the moment of purchase.

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2. Getting started
The following is a list of standard items provided with every
TILBA-R:
List of components
TILBA-R demultiplexer with
Option 1: free space input
Option 2: 10 m of multimode iber input
The TILBA-R demultiplexer is shipped from Cailabs ready-to-
use.
The ibers may become tangled during transport and must be
very carefully removed from the transport case.
1. First, loosen the demultiplexer from the transport case,
without removing it.
2. Next, carefully take out the demultiplexer and the ibers at
the same time. Be careful not to damage the ibers when
removing the units from the transport case.
3. Then, place the TILBA-R on your optical table or desi-
gnated area.
4. Gently clean the single-mode iber optical connectors at
the input and output ports of the units before use.
Unpacking

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3. Product overview
Description
Intended for free space optical communication, the TILBA-R is
an optical device designed to improve the reliability of the optical
link at reception in the presence of atmospheric turbulence or
pointing errors.
TILBA-R is a Multi-Plane Light-Conversion (MPLC) based
spatial demultiplexer that decomposes a beam wave-front
proile into a limited number of spatial modes. The modes are
collected and sent to a single-mode iber.
Operating instructions
The TILBA-R demultiplexer is ready for use.
1. Connect your input signal single-mode ibers to the
corresponding LC connector.
2. Verify the properties of the TILBA-R with the alignment
procedure. The properties should match the performance
report.
Example of intensity proile of Hermite-Gaussian modes.
The below speciications are for a typical TILBA-R device and
may vary for each speciic purchase order.
Speciications
TILBAR RECEIVER OPTICAL PARAMETERS
PARAMETERS TYPICAL VALUE AT 20°C COMMENTS
Number of spatial mode diversity Between 6 and 15 Up to 45 modes
Wavelength of operation C-band Other wavelenghts available
Signal output iber SMF -28e+ or polarization maintaining
SMF PM ibers require free space input
Signal input
Standard 50/125 MMF (OM2) Other ibers available
Free space input Collimated free space
Insertion loss <3 dB -

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Mechanical drawing

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4. Free space alignment
Back-to-back in a single MUX/DEMUX coniguration
The irst step is to align a single multiplexer in a back-to-
back measurement. The light coming from the multiplexer will
be sent to a mirror and back to the system being used in the
demultiplexer coniguration.
Minimum material:
• Light source at the required wavelength
• Light circulator
• PowerMeter
• Mirror
• Lens
• Infrared detector card
Recommended material:
• Optical switch
• Multichannel power meter
• Circulator on each channel
Sending the light back to the system will enable the
measurement of insertion losses and the basic functionality of
the multiplexer.
Depending on the material available, possible options are Figure
1 with only 1 lens, or Figure 2 with two lenses. We recommend
option 2 with two lenses as it gives more lexibility and precision.
It also makes it easier to view the light with an infrared card.
MPLC
L1 M1
Mirror to relect the light
Colimated beam at the
output of the multiplexer
Lens to focus the light on
the mirror
Figure 1: Illustration of a single MPLC measurement using a single lens.
MPLC
L1 M1
Mirror to relect the light
300 µm radius waist colimated beam
at the output of the multiplexer
Two lenses used as a telescope to adapt
the beam size.
L2
Figure 2: Illustration of a single MPLC measurement using two lenses.

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Also, depending on the material used, you will be able to measure
either the crosstalk sum in real-time or only the maximum power.
Measuring the crosstalk helps, but an accurate alignment can
be done without it.
Step 1: Speed check the fundamental beam. Turn on the
source and power the fundamental mode. Note that the
channel labels are indicated on the device and the performance
report. Using a detector card, make sure that the device is well
powered. In a standard component, the waist radius is 300
µm, meaning that the spot is small. You should see a Gaussian
beam. If this is not the case, check the channel labels and the
proile of the other modes.
Step 2: Speed check the modes. Illuminate all modes one by
one. Verify that, at irst sight, the proile of the model agrees
with that of the performance report.
Step 3: Prepare the setup. In coniguration 1 or 2, L1 should be
positioned in a 1-x platform to align the focal point and/or the
telescope. Also, make sure that the light goes right through the
middle of the lens to avoid aberration. M1 should be positioned
on a kinematic mount with at least 2 degrees of freedom.
Step 4: Align the beam. Use the circulator on the fundamental
channel. The objective is to send light and to measure the
power relected by the mirror and demultiplexed in the same
mode. With the fundamental mode on, play on the orientation
of M1 and position of L1 to optimize the received power on the
fundamental mode. A irst rough alignment can be performed,
which rapidly becomes very sensitive.
At the best alignment position, insertion losses for the
fundamental mode should be close to the value on the
performance report x2.
If a multi-channel power meter is available, this enables the
crosstalk with the other channels to be measured. This makes
the alignment easier, as in the optimum position the sum of
all crosstalks from the fundamental mode to the higher order
modes should be at a minimum.
Step 5: Measurements. In this step and when you are happy
with the alignment, you can measure the system performance
for each channel: Insertion loss and crosstalk as indicated in
the annex.
Back-to-back measurement with a MUX and DEMUX
coniguration
Step 6: Measurement of the second MPLC. Repeat steps 1 to
5 for the second MPLC.
Step 7: Prepare the back-to-back setup. In the coniguration
of 2 MPLCs, it is recommended to have 2 telescopes, one after
the MUX to increase the size of the beam, and the other before
the DEMUX. Even if the 2 MPLCs are close to one another,
the beam will have a small divergence leading to a larger beam
size at the DEMUX input. Using 2 telescopes ensures that the
beam is the right size at the reception side and facilitates the
alignment process. The alignment procedure is then similar to
that of a single MPLC except that the circulator is no longer
needed.
MPLC 1
MUX
L1
M1
300 µm radius waist colimated beam at
the output of the multiplexer & input of
the demultiplexer
Two lenses are used as a
telescope to adapt the beam size.
L2
MPLC 2
DEMUX
L3
M2
L4
A small divergence will occur during
propagation. Adpating the 2nd telescope
ensures to have the correct beam size
Figure 3: Illustration of a back-to-back coniguration.

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5. Crosstalk and coupling
eiciency calculation
Calculation of coupling eiciency
Data measured:
• Input power, given by an array Pin(i) corresponding to the
input power on channel i
• Output power, given by a matrix Pi-j corresponding to
the output power on channel jwhen the light is on input
channel i
Method
The coupling eiciency for the full MUX + DEMUX pair for
channel i is equal to: η(i) = Pi-i / Pin(i)
Calculation of crosstalk
Method for obtaining normalized crosstalk
• The transmission matrix obtained by the measurement
depends on the input powers and losses; it does not
correspond to the normalized crosstalk matrix.
• The normalized cross-talk matrix for the MUX + DEMUX
pair XTi-j is obtained by:
XTi-j = Pi-j / Pi-i
This operation cancels the dependence on the input powers and
the optical losses (which are identical to Pi-i and Pi-j ).

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6. Cleaning and maintenance
Cleaning instructions
Under normal operating conditions, the TILBA-R requires very
little maintenance.
Follow the normal procedure to clean the LC/PC optical
connectors of the input and output single-mode ibers.
The housing of the TILBA-R can be cleaned with an optical wipe
dampened with propanol. Do not get the housing wet, it is not
watertight.
Store the TILBA-R in a dry and clean environment, at a normal
temperature (15°C ~ 25°C).
Do NOT open the lid and attempt to clean the inside of the
TILBA-R housing. This is considered disassembling the unit and
thereby voids the warranty.
Troubleshooting
The TILBA-R is a passive device and rarely constitutes a point
of failure.
If you observe an abnormal amount of loss in the systems, clean
the LC/PC connectors of the input and output single-mode
ibers, as normal.
Verify that nothing heavy is constraining the housing of the
TILBA-R.
If you observe an abnormal amount of cross-talk between
channels transported by diferent mode groups, verify the
bending of the iber if you have a ibered option. The iber
should not be bent below a radius of curvature of 10cm. If you
have a free space input option, please refer to the alignment
procedure.
If problems persist, please consult our support service:
Email: [email protected]
Phone: [phone]
Website : www.cailabs.com/en/contact

38 boulevard Albert 1er
35200 Rennes, France
www.cailabs.com
[e-mail]
@CAILabs
CAILABS