Appendix 3. Reuse of Existing Multimode Optical Fiber Cable
App.3-1
TI 30A10A30-01E
Appendix3.ReuseofExistingMultimode
OpticalFiberCable
Compared with single-mode optical fiber, multimode optical fiber has a parameter of modal
bandwidth that limits the transmission distance for high speed signal. We strongly recommend
single mode optical fiber for Vnet/IP that requires high speed 1-Gbps communication. In cases
where existing multimode optical fiber cables have to be reused by reason of the cable installing
cost, follow the precautions shown below, depending on the corresponding cable lengths.
Cable length shorter than 0.55 km
Use GRVSW-675FA (M-SFP-LX/LC) or GRVSW-676FA (M-SFP-LX/LC EEC) transceivers.
These models comply with 1000BASE-LX that meets Vnet/IP requirements.
1000BASE-LX is designed for single-mode optical fiber connection.
Connect a mode-conditioning patch cord to the optical output of these SFP modules in order to
scramble optical transmission mode.
Cable length between 0.55 and 4 km
A multimode fiber cable that is longer than 0.55 km cannot support 1-Gbps communication
speed complying with IEEE802.3x. The long multimode fiber cable cannot be reused unless the
interface speed is downgraded. However, the following restrictions are caused by downgrading
the speed to 100 Mbps.
Restrictions
- Open communication on Vnet/IP is not available. (*1)
- Not applicable to large-scale systems. (*2)
- The time synchronization accuracy of the network time in the same domain, which is usually
±1 millisecond, is degraded to ±3 milliseconds.
- Upgrade the Vnet/IP firmware for all stations in the system to Revision 16 or later.
*1: Separate the Ethernet as the information bus from Vnet/IP.
*2: Applicable to narrow bandwidth segments such as replacing of optical Vnet repeaters or communication lines in entry-class
systems. For a larger system, consult your nearest representative.
Use GRVSFP-674FA (M-FAST SFP-MM/LC) complying with 100BASE-FX to downgrade the
speed to 100 Mbps. This SFP module can connect to a multimode fiber directly, and supports
maximum 4 km transmission distance, under the condition of the following cable characteristic.
- Total optical attenuation at 1310 nm wavelength: 5 dB or less
- Modal bandwidth at 1310 nm wavelength: 800MHz •km or more
However, the characteristic at 1310 nm wavelength of the old existing multimode fiber may be
unknown or insufficient. The following pre-evaluation of the performance by using actual SFP and
L2SW is necessary to confirm the communication quality.
Feb. 29, 2016-00
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