Network Card User Manual

MRV Communications, Inc. – Installation Manual

TereScopes Bench Test Procedure

Introduction

All TS Products are bench tested indoors prior to outdoor

installation to ensure that the system is fully functional.

The bench test is a simple procedure whereby a link pair is aligned

on the table and activated to simulate a channel of communication

(see fig.1).

2 Points to Remember

1. Since the link distance during the bench test is very short (i.e. the

devices activated are very close), the receivers will go into saturation

unless the signal is attenuated. (NOTE: In the 700/G, deep into

saturation the DVM reading may actually drop back down, giving

the false impression that the link is misaligned. It is therefore

vital to place the attenuator in the link path before optimizing

alignment.)

To avert entering saturation, the transmit signal must be physically

attenuated.

We recommend the simple procedure of inserting a piece of paper

or the like into the beam path, or concealing a portion of the beam

with an opaque (non-transparent) material. This will reduce the

signal power entering the receiver.

Make sure to attenuate the signal enough so that the receiver’s

optical power meter value falls below the saturation estimate of the

device. See table below for saturation estimate.

2. An additional derivative of the short link distance is the presence

of reflections.

The signal will reflect off the front window of the receiver back at

the transmitting device and may be mistaken as part of the opposite

transmission.

This interference is commonly called “cross talk”.

To avoid cross talk during the bench test, it is advisable to check

whether interfering reflections exist by shutting off power to one

device and verifying that the optical power meter reading in the

other (active) device is zero.

This should be repeated for the opposite device.

Alternatively, a practical setup for bench testing the 4” series

(models B, C and D) and Light series (models A and C2) is

presented in Figure 1; the bench test setup for the 10” series

(models E and F) is presented in Figures 2a,2b.

In the 4”/Light setup, a thin physical barrier, such as a piece of

cardboard, is used as a wall to divide between the beam paths, thus

ensuring that no cross talk occurs.

In the 10” setup, the two devices are not centrally aligned; instead,

only one corner of each device faces the opposite device. This

APPENDIX E