Single Mode to Multi-Mode
Fiber Optic Converter

Model 279 - Reference Manual

Table of Contents

1.0 General Description
2.0 Specifications
3.0 Installation
4.0 Operation
5.0 Troubleshooting
6.0 Power

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1.0 General Description

The Model 279 provides transparent conversion between fiber optic devices utilizing multi-mode fiber and those with single mode fiber. Single mode fiber can transmit data over much longer distances than is possible with multi-mode fiber. However, both fiber types have their place. Multi-mode is well suited to short premises installation, while single mode fiber is ideal for longer "metropolitan distances."
Single mode fiber accomplishes the distance advantage by confining the transmitted power to a single optical mode which propagates down the center axis of the fiber. As a result, power lost through leakage in the fiber walls is eliminated. The converter regenerates signal strength and is mainly used to exceed the distance specification for multi-mode fiber. The Model 279 can also be used when the optical fiber type specified by the equipment is not compatible with the installed fiber optic cable.
The Model 279 includes ability to operate from DC to 2.5 MBPS. A loss budget of 15 dB it is provided which equates to a distance of approximately 20 kilometers.

2.0 Specifications

2.1 Interface
Multi-mode-850nm, full duplex
Single mode-1300nm, full duplex

2.2 Connectors
Single mode-ST

2.3 Data Rate : 0 to 2.5 MBPS

2.4 Loss Budget
15dB max @ 1300nm on 9/125um cable
12dB max @ 850nm on 62.5/125 cable

2.5 Switches
Line Loss - Adjusts to best performance of single mode fiber for losses of 2, 5, 10 or 15 dB.
Phase - Allows reversal of phase between signals of multi-mode and single mode systems.

2.6 Indicators : TD and RD LED's and Line Loss selection LED's

2.7 Power : +12 Volts DC. Supplied by wall mount adapter, 110 Volts- 60 Hz standard, 220 Volt-50 Hz optional. A DC adapter Model 1510-0037 is also available that allows operation from a DC source whose voltage is within the range of +18 Volts to +36 Volts.

2.8 Size : 7"W x 3"H x 1"D (177.8mm x 76.2mm x 25.4mm)

2.9 Environment
Operating temperature-0 to 50 C
Storage temperature- -5C to +75C
Relative humidity-5% to 95%, no condensation

3.0 Installation

3.1 Physical Mounting
The Model 279 can be mounted in any position. Care should be exercised when routing the fiber optic cables. The minimum bend radius of 2" for the cables should not be exceeded. The Model 279 is provided with 2 mounting holes to allow the unit to be attached to any position.

3.2 Installation
The Model 279 is designed to interface between single mode and multi-mode fiber systems. Cables used to attach to the Model 279 should be terminated with ST connectors. Power for the Model 279 is derived from the supplied wall adapter. This power supply is plugged into the Model 279 using the 1.3 millimeter power jack.

4.0 Operation

In fiber optic systems that do not offer DC response there usually is a clock signal which is always being transmitted. The presence of this clock signal allows automatic gain control circuitry to adjust the gain of the receiving amplifier to compensate for single mode cable loss. Since the Model 279 can operate at DC it is necessary to establish a different method to compensate for the length of the single mode cable. In the Model 279 this is accomplished using a four position switch, called Line Loss to allow selection of amplifier gain to accommodate single mode cable losses of 2, 5, 10 and 15 dB. These losses approximate cable lengths of 3, 7.5, 15 and 20 kilometers respectively. The method of setting the switch is as follows:
With the Model 279 installed set the line length switch to the position where the received data is no longer detectable. Then position the switch to the previous dB loss position. Since the switch position is not apparent the selection will be indicated on the LED display.
In addition to the Line Loss switch the user has the ability to change the phase of the signals going between the multi-mode and single-mode equipment. When no data is being transmitted, the TD and RD indicators will either be both on or both off. If one is on and the other off then the phase of the signals is incorrect and the switch position should be changed. The switch is either In phase or Out of phase. Note: The data LED's are not marked since the functions of TD (transmit data) and RD (receive data) are arbitrary depending on the users implementation.

5.0 Troubleshooting

The following is a list of possible problems that may arise during the installation and solutions to these problems:

1. The data being received is garbled?
a) The Line Loss switch is not set for the loss of the cable (see section 4.0)
b) The Phase switch is not set properly (see section 4.0)

2. No data is being received.
a) Customer equipment not connected to the unit.
b) The transmit and receive cables are improperly connected.
c) The power adapter is not connected.
d) Link connection exceeds maximum specified distance.
If the unit is believed to be defective, operation can be verified if one of the devices to which the converter is attached is capable of operating in a full duplex mode (such as a terminal). Connect a loopback, short fiber cable of the correct type, between the T and R fiber connectors, and verify data transmission.
If the Model 279 is functioning correctly, any data entered on the keyboard should appear on the screen.

6.0 Power
Power for the Model 279 is supplied by a wall adapter that generates +12 Volts DC. The wall adapter is available for 110 Volts, 60Hz or 220 Volts, 50Hz. The part numbers are:
110 Volts - 1505-0033
220 Volts - 1505-0034
For applications where only DC voltages are available Telebyte offers its DC Adapter, Model 1510-0037, which accepts a voltage source of +18 Volts to +36 Volts and generates the required +12 Volts needed by the Model 279.

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