Test Access Solutions

There are four main parts to a Test Access Solution for copper line or Fibre Optic Testing.

Management

The management system controls the Test device and Access Switch. It also provides the interface to the remote user and can control queues at busy times. It is possible the Test Head and Access Switch have their own management control and these are dealt with by the operators control system at a higher level.

Test Head

A test head is required to carry out the copper line testing or Optic Fibre test. The complexity and functionality of these units vary between manufacturers, as does the price. The Test section can be treated as a seperate part of the whole scenario and it is feasible to mix and match different suppliers for each part.

Access Switch

The Access Switch is the physical device for connecting into the network. Copper lines generally use a bank of relays that sit in series with the circuit and switch when given commands from a control system. In Fibre networks the access is via a  Wavelength division multiplexer (WDM) or a good quality PLC Splitter. The function of the Access Switch is to route the network up to the test device.

Network

The network will be a copper or Fibre. Copper line circuits are a pair of wires between the customer and the exchange (Central Office) distributed via street cabinets and telegraph poles.

Fibre networks are usually accessed at the Optical Distribution Frame (ODF) and test out to the customers Optical Network Unit (ONU)

Lets explore the full solution in more detail. For clarity I will split out into two sections - 1: Copper Testing 2: Fibre Testing and use the products produced by UTEL as a reference.

Test Head

Test Heads are all different and the level of testing will depend on the functionality offered by the unit.

Typically it will do all the basic tests that could be performed with a Volt meter. Earth on A or B leg, resistance, loop, dis, capacitance, ac/dc voltages etc.

It will also have a number of test buses, two wire or four wire. Four wire allows the circuit to be split and the test head to look 'out' and 'in'.

The Test Head can also have an internal modem that can be connected to the line to test the customers modem or DSLAM port.

Test Access Switch Matrix (TASM)

The Test Access Switch Matrix (TASM), also known as the Test Assess Matrix (TAM) is the physical switch breaking into the copper line. The copper line pair (2 wires) is now split and diverted up a test bus as four wires, two wires looking one way (In) and two wires looking the other way (Out).

The TASM or TAM can be matched to a DSLAM port and will access 8, 16, 32, 64 or 72 lines that the vendor dictates. A universal shelf TASM is also available and matches the connecting blocks, 64, 100 or 128 circuits.

Test Access Switches can be fitted at installation time or retro fitted as required.

Management System

UTEL supply a management system called an Intelligent Switch Matrix Controller (ISMC). Most Central Office sites will only need one ISMC. It is possible to connect a second ISMC as a slave for extremely large or fragmented sites.

This device is the connection to the outside world, Test Head and Test Access Matrix. Connection is usually over an IP network and then onto the TASM and TAMs via Cat5 cable.

Installation is simple and initial configuration is performed on site using a laptop in the MMI port. UTEL supply free configuration software that can also produce a commissioning report to prove a successful installation has been performed.

Optical Time Domain Reflectometer (OTDR)

The OTDR is used to test Fibre Optic cables and are commonly used for fault finding. Every manufacturer offers different features and the feature-rich variants tend to be larger and rack mounted in a Central Office location. Smaller hand held units offer less options but are light and portable.

The OTDR is connected to the Fibre cable via a Wavelength Division Multiplexer (WDM) or 2x2 Splitter. Adding multiple Optical Switches into the circuit increases the access the OTDR has to the network.

The OTDR can also be configured to manage the Optical Switch and provide the IP access for control.

Optical Test Access Switch

The Optical Switch increases the number of Fibre cables available to the OTDR. The switches can be 'stacked' with the first one being connected to a further 60 units giving access to over 3000 fibres. As the losses are low through the unit it is possible to add further stages to this.

Optical Test Switches from UTEL are available in 36, 60 and 120 ports.