Appendix 4. Precautions for Long-haul Optical Fiber Connection
App.4-1
TI 30A10A30-01E
Appendix4.PrecautionsforLong-haul
OpticalFiberConnection
Distance between the two arbitrary stations in a domain
The specification of Vnet/IP has a limitation of communicable distance between the two arbitrary
stations in a domain. The maximum distance (40 km) is too short for the network configuration
requiring long-haul optical fiber connection. This section shows a rule to relax this limitation
based on the origin. Please follow this guideline in case of the long-haul connection in a domain
exceeding 40 km.
Theruleforlong-haulconnectioninadomainexceeding40km
Low latency network configuration is mandatory for real-time communication on Vnet/IP.
Therefore, Vnet/IP prescribes two limitations to ensure real-time communication:
(1) Maximum number of L2SW cascading in a domain: 7
(2) Maximum distance between the two arbitrary stations in a domain: 40 km
Because these two limitations are intended to reduce the network latency, the maximum
communicable distance in a domain can be extended by reducing the number of cascaded layer
2 switches. This relationship is shown in the following table.
However, the long-haul connection exceeding 40 km degrades the time synchronization
accuracy of the network time in the same domain to ±3 milliseconds.
Number of
cascaded L2SW
7 6 5 4 3 2 (*1)
Max.communicable
distance in a domain
40 km 60 km 80 km 100 km 120 km 120 km
*1: Multiple long-haul optical fiber connections is not supported, so the maximum distance depends on the performance of the SFP.
PrecautionsforuseofSFPforlong-haulapplying1550nmwavelength
Typical single-mode optical fiber cable complying with IEC 60793-2-50 B1.1, ITU-T G652.B,
or JIS C 6835 SSMA is applicable for the wavelength of either 1310 nm or 1550 nm. However
it is optimized for 1310 nm wavelength. To get the maximum performance with the GRVSFP-
696FA (M-SFP-LH/LC, up to 80 km) or GRVSFP-697FA (M-SFP-LH+/LC, up to 120 km), the
performance of the optical fiber cable must meet the following specifications:
(1) Cable attenuation at 1550 nm wavelength: 0.25 dB/km or less
(2) Chromatic dispersion at 1550 nm wavelength: 19 ps/nm/km or less
Use the specific optical fiber, such as Dispersion Shifted Fiber (DSF), that is optimized for 1550
nm wavelength because the typical single-mode fiber does not satisfy above specifications.
Feb. 29, 2016-00
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