Cabletron Systems EMM-E6 Ethernet Manual De Usuario

When connecting a single mode fiber optic link segment to the hub (via 
EPIM-F3), ensure the network meets the following requirements:

•

Cable Type - Fiber optic link segments should consist of 8/125 to 

12/125 

µ

m single mode fiber optic cabling. You can also use 

62.5/125 

µ

m multimode cable with the EPIM-F3; however, 

multimode cable has greater optical loss, and limits the possible 
distance to 2 km.

•

Attenuation - You must test the fiber optic cable with a fiber optic 

attenuation test set adjusted for a 1300 nm wavelength. This test 
verifies that the signal loss in a cable falls within the acceptable level 
of 10.0 dB or less for any given single mode fiber optic link.

•

Budget and Propagation Delay - When you determine the 

maximum fiber optic cable length to incorporate fiber runs into your 
network, you must calculate and consider the fiber optic budget (a 
total loss of 10.0 dB or less is permissible between stations) and total 
network propagation delay.

To determine the fiber optic budget, combine the optical loss due to 
the fiber optic cable, in-line splices, and fiber optic connectors. 
Typical loss for a splice and connector (together) equals 1 dB or less.

Network propagation delay is the amount of time it takes a packet to 
travel from the sending device to the receiving device. Total 
propagation delay for the entire network must not exceed 25.6 

µ

s in 

one direction (51.2 

µ

s round trip). If the total propagation delay 

exceeds 25.6 

µ

s, you must use bridges.

•

Length - If you meet all system budgets, the maximum single mode 

fiber optic cable length can reach 5 km (3.1 miles) with bridges at 
each segment end. However, IEEE 802.3 FOIRL specifications 
specify a maximum of 1 km (1093.6 yards).

CH1Book  Page 5  Wednesday, March 20, 1996  7:48 AM