Cabletron Systems NBR-420, NBR-220, NBR-620 manual C.1.3 Single Mode Fiber Optic Network

Appendix C: Network Planning and Configuration

-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 allowed for the entire network must not exceed

25.6∝s in one direction (51.2 ∝s round trip). If the total propagation delay between any two nodes on the network exceeds

25.6∝s, you must use bridges.

•Length - The maximum possible multimode fiber optic cable length is 2 km (2187.2 yards). However, IEEE 802.3 FOIRL specifications specify a maximum of 1 km (1093.6 yards).

C.1.3 Single Mode Fiber Optic Network

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

•Cable Type - Fiber optic link segments should consist of

8/125 to 12/125 ∝m single mode fiber optic cabling. You can also use 62.5/125 ∝m multimode cable with the EPIM-F3; however, multimode cable allows for 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.

Page C-4 NBR-SERIES Installation Guide