H.4
Calculating maximum fiber cable length
Maximum optical fiber length is determined by two major factors: optical loss
and bandwidth limit. These types of optical fiber performance and quality are
defined in the ISO standard ISO/IEC 11801.
OMx/OCx = ISO/
IEC 11801
standard
(optical fiber type)
For
wave
-
length
Optical
power
budget
Cable loss Coupler
loss.
ANSI/TIA/
EIA
-
568
-
A
BW Length
limit
OM1 = Multi Mode
62.5/125 µm
850 nm 8 dB
-
3.5 dB/km
-
0.75 dB
200
MHz*km
OM2 = Multi Mode
50/125 µm
850 nm 8 dB
-
3.5 dB/km
-
0.75 dB
500
MHz*km
OM3 = Multi Mode
50/125 µm laser
optimized fiber
850 nm 8 dB
-
3.5 dB/km
-
0.75 dB
2000
MHz*km
OM4 = Multi Mode
50/125 µm laser
optimized fiber
850 nm 8 dB
-
3.5 dB/km
-
0.75 dB
4700
MHz*km
OS1 = Single Mode
9/125 µm
1310 nm 10 dB
-
1 dB/km
-
0.75 dB
N/A
OS2 = Single Mode
9/125 µm
1310 nm 10 dB
-
0.4 dB/km
-
0.75 dB
N/A
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 the maximum length of optical
cable can be done in the following manner:
Optical budget GHS system
850 nm
: 8 dB
Maximum fiber cable length
:
L
optical
(km)
Fiber cable loss
:
-
3.5 dB/km
Number of couplers
: c
Coupler loss
:
-
0.75 dB
Safety margin for aging and repair :
-
3 dB
L
dB
dB
dB
dB
km
optical
+ (
c
* 0.75
+ (
3 5
.
(
)
−
−
−
−
GEN3i
I3763-3.1 en HBM: public
945