Page 222 - Sensors and Control Systems in Manufacturing

Fiber Optics in Sensors and Contr ol Systems

FIGURE 3.64 Hybrid fi ber network. 183

• Signal propagation delay. Allowable system signal propagation
delay may limit the overall distance of the fiber network.

Example.
Electrooptic module distortion = 50% allowable distortion
× 1 Mbaud transmission
= 50 ns
Calculate:

–6
Allowable distortion = 50% allowable distortion × 10 = 500 ns
Maximum number of repeater sites = 500 ns/50 ns = 10

N OT E :
NOTE: A star coupler counts as a repeater site.
Distance Calculation (Signal Propagation Delay)
Delay of light in fiber-optic regeneration 1.5 ns/ft
Delay in module 50 ns

Manufacturers of programmable controllers will provide the value of
the system delay. This value must be compared with the calculated allow-
able delay. If the overall fiber system is longer than the published maxi-
mum length of the wired system, the system must be reconfigured.