H Using Fiber Optic Cables; Calculating Maximum Fiber Cable Length - HBM Genesis GEN5i User Manual

H Using Fiber Optic Cables

564
H.1

Calculating maximum fiber cable length

Maximum optical fiber length is determined by two major factors; optical loss
and bandwidth limit. These type of optical fiber performance and quality are
defined in ISO standard ISO/IEC 11801.
OMx/OCx = ISO/
IEC 11801
standard
(optical fiber type)
OM1 = Multimode
62.5/125 µm
OM2 = Multimode
50/125 µm
OM3 = Multimode
50/125 µm laser
optimized fiber
OM4 = Multimode
50/125 µm laser
optimized fiber
OS1 = Singlemode
9/125 µm
OS2 = Singlemode
9/125 µm
Note Table shows worst case specifications.
Standard GHS systems use VCSEL 850 nm optical transmitters/receivers, they
have an optical power budget of 8 dB. Calculating maximum length of optical
cable can be done in the following manner:
Optical budget GHS system
850 nm
Maximum fiber cable length
Fiber cable loss
Number of couplers
Coupler loss
Safety margin for aging and repair
For Optical Cable loss Coupler
power
wave-
budget
length
-3.5 dB/km -0.75 dB
850 nm 8 dB
-3.5 dB/km -0.75 dB
850 nm 8 dB
-3.5 dB/km -0.75 dB
850 nm 8 dB
-3.5 dB/km -0.75 dB
850 nm 8 dB
-1 dB/km
1310 nm 10 dB
-0.4 dB/km -0.75 dB
1310 nm 10 dB
:
:
:
:
:
:
GEN5i
BW Length
loss. limit
ANSI/TIA/
EIA-568-A
200
MHz*km
500
MHz*km
2000
MHz*km
4700
MHz*km
-0.75 dB
N/A
N/A
8 dB
L (km)
optical
-3.5 dB/km
c
-0.75 dB
-3 dB
I2679-4.0 en