FIBEROPTIC SENSOR TECHNOLOGY HANDBOOK

55/125 pm, F.4uI-TIMODE,
Gl, OPTICAL FIBER \
EL BUFFER TO
D. OF 1.02 mm
‘r
4
15 CU-CLAD-STEE
WIRES – EACH 0.
0. D. – AS HELIX
;KET TO 2.54 mm
Fig . 6.24 A cross section of one of a large number of
different electrooptic cable designs.
cable fiberoptic repeaters is determined by the risetime
and power budgets, which in turn, depend on attenuation
and cable length-between-repeaters. An example
of a fiberoptic electrooptic repeater is shown in Fig.
6.25. This repeater handles a high bit-rate in one di-
24
Fig. 6.27
~
01 1000
FREQUENCY (MHz)
The optical power loss per hertz for one
kilometer lengtha of several types of cables
at various frequencies.
6.3.3 Multiplexing with Optical Fibers
Multiplexing may be accomplished with optical
fibers in the following ways:
HBR(A,)
TOPROCESSING— OPTCAL
— STATION — DuPLEXER
Fig. 6.25
+=+
LSR(A2)
OPTICAL
DU~ER —
LSR
H=?HSR
OTHER REKATERS
h example of a fiberoptic full duplex repeater.
rection for user data and a low bit-rate in the other
direction for control and supervisory data in a single
fiberoptic cable. An arrangement for the optical duplexers
that was shown in Fig. 6.25 is sho~ in Fig.
6.26.
FREQUENCY -DIVISION MULTIPLEXING (FDM)
Modulate a single optical wavelength with a different
carrier frequency for each channel.
WAVELENGTH-DIVISION MULTIPLEXING (WDM)
Use two or more optical sources each with a different
wavelength for each channel.
TIME-DIVISION MULTIPLEXING (TDM)
Different time-slot for each channel.
sPAcE-DIvxsIoN MULTIPLEXING (fiDM)
Different fiber for each channel.
POLARIZATION
Different form of polarization for each channel.
The multiplexing scheme that is used for a
given application depends on the number of channels required
and the cost factors for each scheme. A typical
multiplexing arrangement is shown in Fig. 6.28. In
TOHSR
RCVR
Fig. 6.26
. . ()
. ---
_HSR
6 Q A, .
_LSR
A2 Q
‘
----
~.
p
AZFROM
--- LSRXMTR
‘- ‘- ““-~%1:
DICHROIC
FILTER
An arrangement for a fiberoptic duplexer.
m
2
1
$
Fig. 6.28
SENSOR
ARRAY
TRANSMl~ER
IJULILS,GNAL / \ ( /
-’45-J ‘RECE’VER
AQQ.. nlln
An example of a fiberoptic sensor lineararray
telemetry system with single optical
repeatered cable return.
tin indication of the power-loss-per-hertz
versus frequency for an optical fiber, compared to wire
pairs and coaxial cables, iS sbo~ in Fig. 6.27. Note
that in the graded-index fiber the loss-per-hertz is
almost independent of frequency for frequencies up to
almost one gigahertz.
this figure, the signals from the sensor array are
multiplexed on a time-division multiplexing (TDM) basis
so that only one series of repeaters is required for a
single fiber. This basic fiberoptic link consists of
a fiberoptic transmitter (modulated light source), a
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