This document discusses fiber optic splicing and demountable fiber optic connectors. It explains that fiber splicing creates a permanent joint between two optical fibers, while demountable connectors allow for repeated connection and disconnection but require more precise alignment to maintain efficiency. Different types of fiber optic couplers are also presented, including fused biconical taper couplers, micro-optics couplers, and waveguide couplers. Wavelength division multiplexers and demultiplexers are distinguished from fiber optic couplers. Channel spacings for dense wavelength division multiplexing, wavelength division multiplexing, and coarse wavelength division multiplexing are defined.

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• A permanent joint formed between two
individual optical fibers in the field or factory
is known as a fiber splice.
• Fiber splicing is frequently used to establish
long-haul optical fiber links where smaller
fiber lengths need to be joined.
• There is no requirement for repeated
connection and disconnection.
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• Demountable fiber connectors are more difficult to achieve
than optical fiber splices. This is because they must maintain
similar tolerance requirements to splices in order to couple
light between fibers efficiently, but they must accomplish it in
a removable fashion.
• Also, the connector design must allow for repeated
connection and disconnection without problems of fiber
alignment, which may lead to degradation in the performance
of the transmission line at the joint.
• Hence to operate satisfactorily the demountable connector
must provide reproducible accurate alignment of the optical
fibers.
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Fused biconical taper (FBT) coupler
Micro-optics coupler
Waveguide coupler
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• Fixed for one wavelength also known as
achromatic coupler
• Coupler designed to work for two or more
wavelengths simultaneously also known as
WDM coupler
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• Excess loss
• Insertion loss:
Port 1 to 3
Port 1 to 4
• Crosstalk
• Split ratio
4
3
1
log
10
P
P
P
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3
1
log
10
P
P
4
1
log
10
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P
1
2
log
10
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P
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 4
3
3
P
P
P
1
2
3
4

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1. Polymer on silica
2. Polymer on silicon
3. Silica on silica
4. Silica on silicon

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A four-port multimode fiber FBT coupler has 60
μW optical power launched into port 1. The
measured output powers at ports 2, 3 and 4 are
0.004, 26.0 and 27.5 μW respectively.
Determine the excess loss, the insertion losses
between the input and output ports, the
crosstalk and the split ratio for the device.
Answers: 0.5 dB, 3.63 dB, 3.39 dB, −41.8 dB, 48.6%.
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Example

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• The splitting loss is related to the number of
output ports N following:
• For a single input port and multiple output
ports where j = 1, N, then the excess loss is
given by:
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• MUX – combines several wavelength into
one fiber.
• DEMUX – separates several wavelength.
Coupler- combines signal at the same
wavelength and a WDM MUX couples
different wavelength.

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Channel spacing:
DWDM 0.4 nm (50 GHz)
WDM 0.8 nm (100 GHz) and 1.6 nm (200 GHz)
CWDM 20 nm
  .
50
1550
10
3
4
.
0
2
8
2
GHz
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c
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f
f
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


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