The figure below 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 additional 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.
The UR-series IEEE C37.94 communication modules (modules types 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 stand-
point 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
The specifications for the module are as follows:.
IEEE standard: C37.94 for 2 64 kbps optical fiber interface (for 76 and 77 modules)
Fiber optic cable type: 50 mm or 62.5 mm core diameter optical fiber
Fiber optic mode: multi-mode
Fiber optic cable length: up to 2 km
Fiber optic connector: type ST
Wavelength: 830 ±40 nm
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 as shown below.
Figure 3–40: G.703 AND FIBER INTERFACE CONNECTION
L90 Line Current Differential System
3.3 PILOT CHANNEL COMMUNICATIONS
3.3.8 G.703 AND FIBER INTERFACE
3.3.9 IEEE C37.94 INTERFACE