User Manual

ADCP-75-159 • Issue 1 • August 2003 • Section 1: Overview

Page 1-7

signal is digital, the input and output RF signal levels at the HU or the RU are not dependent on

the level of the optical signal or the length of the optical fiber. A diagram of the fiber optic

transport system for a typical Digivance system is shown in Figure 1-6. The Digivance 20 Watt

system does not support reverse path diversity at this time.

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

fiber and the losses imposed by the various connectors and splices. The SMR Digivance system

provides an optical budget of 17 dB (typical) when used with 9/125 single-mode fiber.

Figure 1-6. Standard Fiber Optic Transport

In some applications, it may be desirable or necessary to combine the forward path and reverse

path optical signals from a single HU/RU pair onto a single optical fiber. This can be

accomplished by using a passive bi-directional Wavelength Division Multiplexer (WDM)

system. The optical wavelengths used in the Digivance system are 1550 nm for the forward path

and 1310 nm for the reverse path. Because the Digivance system uses different optical

wavelengths for the forward and reverse paths, both signals can be combined on a single optical

fiber. One WDM module is mounted with the HU and the other WDM module is mounted with

the RU as shown in Figure 1-7. The WDM system is available as an accessory item.

Figure 1-7. Wavelength Division Multiplexer Application

In some applications, it may be desirable or necessary to combine the forward and reverse path

optical signals from multiple HU’s and RU’s onto a single optical fiber. This can be

accomplished by using an active Coarse Wavelength Division Multiplexer (CWDM) system. Up

to four Digivance systems may be configured to operate over a single optical fiber. A CWDM

module is mounted with each HU and RU as shown in Figure 1-8. The CWDM system converts

the optical signal transmitted by each HU and RU to a new optical wavelength that is unique for

each unit. This allows the CWDM system to distinguish between the optical signals generated

by each HU and RU and therefore to distribute those signals to the appropriate destination. The

CWDM system is available separately as an accessory item.

HOST UNIT

18526-A

REMOTE

UNIT

FORWARD PATH

REVERSE PATH

FIBER OPTIC

LINK