User Manual Part 1

Fiber Optic Transport

FlexWave Prism Host, Remote and EMS 5.1 System Reference Page 17

1.6 FIBER OPTIC TRANSPORT

In a typical Prism system the Host is connected to the Remote using two single-mode

optical fibers. One fiber is used to transport the forward pathh optical signal and a

second fiber is used to transport the reverse pathh optical signal. With the diversity

option, the diversity reverse pathh optical signal is sent on the same rev erse path

fiber. (However, the diversity signal can also be transmitted on a separate fiber pair

if more than 12 timeslots are required at a single Remote.) Because the optical signal

is digital, the input and output RF signal levels at the Host or the Remote are not

dependent on the level of the optical signal or the length of the optical fiber. A

diagram of the standard fiber optic transport system for both a non-diversity and

diversity system is shown in Figure 1-9.

The maximum length of the optical links is dependent on the loss specifications of

the optical fiber and the losses imposed by the various connectors and splices. The

system provides an optical budget of 25 dBB (typical) when used with 9/125

single-mode fiber. There must be at least 10 dB of optical loss to prevent over-driving

and possible damage to the optical receiver.

Figure 1-9. Standard Fiber Optic Transport Application

The SeRF (Serialized RF) digital protocol consists of digitized RF, Fast Ethernet, and

Host to Remote communication and management. The protocol provides you with

full access to the 100BASE-T (Ethernet) connection between the Host and each

Remote, and the ability to provision the RF spectrum of the DARTs. The digitized RF

portion of the SeRF protocol is divided into 12 timeslots, with each timeslot

representing roughly 5 MHz of digitized RF spectrum. Utilizing the full 12 timeslots

yields between 60 and 75 MHz of total digitized RF on each SeRF Small Form-Factor

Pluggable (SFP) laser connection.

77073-008

Remote

Unit

Forward Path

Reverse Path

Non-Diversity Fiber Optic Link

Forward Path

Diversity Fiber Optic Link

Reverse Path

And

Diversity Reverse Path

Host

Unit

Remote

Unit

Up To

Eight