Westermo ODW-621, User Manual

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11
6650-2223
Designed for harsh environments, such as industrial, road and railway
applications
The ODW-621 complies with standards for industrial environments, railway signalling and
telecommunications apparatus. Additionally the wide temperature range permits it to be
installed in out-door cabinets without any additional measures, such as heating, etc.
System delay in an optical network
Serial data transferred from one ODW-621 via an optical network to a second one, will
be delayed due to the length of optical fibre and the signal processing within the units.
The signal processing delay is dependent on the data rate and conversions, and the fibre
delay is dependent on the total length of the optical fibre.
Item Functions Delay
1 Fibre:
Optical fibre length delay (typical) 5
μ
s/km
2 Converter electrical to fibre:
Signal processing 0.6
μ
s (CTS mode)
1 t
Bit
+ 0.6
μ
s
(CTS/RTS mode)
3 Converter fibre to electrical:
Signal processing 0.6
μ
s
Note t
bit
= 1 / Baud rate (Baud rate in bit/s)
The system delay when transferring data from the serial input at one ODW-621 to the
serial output of other one is calculated by adding the following:
1. Fibre: The optical fibre length delay.
2. Converter electrical to fibre: Signal processing delay.
3. Converter fibre to electrical: Signal processing delay.
Example 1: Data data transfer from one ODW-621 to a second
converter with a total fibre length of 25 km. Data rate of 9 600 bit/s.
1. Fibre: The total optical fibre length delay 25 * 5
μ
s = 125
μ
s.
2. Converter electrical to fibre: Signal processing delay 1 t
bit
+ 0.6
μ
s = 105
μ
s + 1.0
μ
s
= 106
μ
s.
3. Converter fibre to electrical: Signal processing delay = 0.6
μ
s.
4. The system delay is calculated by adding the delays in items 1 to 3 above = 232
μ
s
Example 2: Data transfer from one ODW-621 to a second converter
with a total fibre length of 25 km. Data rate of 9 600 bit/s.
5. Fibre: The total optical fibre length delay 25 * 5
μ
s = 125
μ
s.
6. Converter electrical to fibre: Signal processing delay = 0.6
μ
s.
7. Converter fibre to electrical: Signal processing delay = 0.6
μ
s.
8. The system delay is calculated by adding the delays in item 1 to 3 above = 126
μ
s