G.703 And Fiber Interface - GE T60 Instruction Manual
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CHAPTER 3: INSTALLATION
The connections shown in the figure are for multiplexers configured as data communications equipment (DCE) units.
3.4.7 G.703 and fiber interface
The following figure shows the combined G.703 plus fiberoptic interface configuration at 64 kbps. The 7E, 7F, 7G, 7Q, and
75 modules are used in configurations where channel 1 is employed via the G.703 interface (possibly with a multiplexer)
and channel 2 via direct fiber. AWG 24 twisted shielded pair is recommended for external G.703 connections connecting
the shield to pin 1a at one end only. For the direct fiber channel, address power budget issues properly. See previous
sections for details on the G.703 and fiber interfaces.
When using a laser interface, attenuators can be necessary to ensure that you do not exceed the
maximum optical input power to the receiver.
3.4.8 IEEE C37.94 interface
The UR-series IEEE C37.94 communication modules (module types 2G, 2H, 2I, 2J, 76, and 77) are designed to interface with
IEEE C37.94 compliant digital multiplexers or an IEEE C37.94 compliant interface converter for use with direct input and
output applications. The IEEE C37.94 standard defines a point-to-point optical link for synchronous data between a
multiplexer and a teleprotection device. This data is typically 64 kbps, but the standard provides for speeds up to 64n kbps,
where n = 1, 2,..., 12. The UR-series C37.94 communication modules are either 64 kbps (with n fixed at 1) for 128 kbps (with
n fixed at 2). The frame is a valid International Telecommunications Union (ITU-T) recommended G.704 pattern from the
standpoint of framing and data rate. The frame is 256 bits and is repeated at a frame rate of 8000 Hz, with a resultant bit
rate of 2048 kbps.
The specifications for the module are as follows:
IEEE standard — C37.94 for 1 × 128 kbps optical fiber interface (for 2G and 2H modules) or C37.94 for 2 × 64 kbps
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optical fiber interface (for 76 and 77 modules)
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Fiber optic cable type — 50 nm or 62.5 μm core diameter optical fiber
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Fiber optic mode — multimode
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Fiber optic cable length — up to 2 km
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Fiber optic connector — type ST
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Wavelength — 820 ±40 nm
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Connection — as per all fiber optic connections, a Tx to Rx connection is required
The UR-series C37.94 communication module can be connected directly to any compliant digital multiplexer that supports
the IEEE C37.94 standard. The figure shows the concept.
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 3-46: G.703 and fiber interface connection
DIRECT INPUT AND OUTPUT COMMUNICATIONS
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