Cabletron Systems EMM-E6 Ethernet - Manual (Page 52)

NETWORK REQUIREMENTS
EMM-E6 User’s Guide 2-5
2.1.3 Single Mode Fiber Optic Network
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