Multimode fiber transmission with OC-3 and OC-12 circuit packs

Overview

The OC-3 and OC-12 circuit packs can transmit signals over Multi-Mode Fiber (MMF). OC-3 and OC-12 circuit packs used on Alcatel-Lucent 1665 DMX are designed to meet or exceed Optical Performance Standards per Telcordia ^® GR-253-CORE on standard Single-Mode Fiber (SMF). This section reflects the results of tests demonstrating successful transmission over shorter distances of MMF. Based on this testing, transmission of OC-3 and OC-12 signals over MMF can be supported by an Alcatel-Lucent 1665 DMX system equipped with LNW37, LNW45, LNW49, LNW50, LNW55, or LNW82 circuit packs within the limits specified.

Core diameters

Standard SMF core diameters are specified to be in the range of 8−10 mm.

MMF core diameters are specified to be 50 mm or 62.5 mm.

Receiver ports

All existing Alcatel-Lucent 1665 DMX circuit pack codes that utilize OC-3 or OC-12 optical interfaces incorporate optical receiver ports that accept optical inputs from fiber cores up to 62.5 mm in diameter. Therefore, the receivers are designed to capture all of the incoming light from both SMF and MMF.

Transmitter ports

The LNW37, LNW45, LNW49, LNW50, LNW55, or LNW82 circuit packs utilize optical interfaces that incorporate laser transmitter ports designed to launch into 8−10 mm SMF. The laser transmitters in these circuit packs are Distributed Feedback (DFB) or Single Longitudinal (SLM) mode lasers.

Recommendations

With multi-mode fiber specified to meet 1 GbE fiber standards per the original IEEE 802.3zTM (now found in IEEE 802.3-2002) and rated at 500 MHz-km or greater, "Single-mode Fiber Offset-Launch Mode- Conditioning Patch Cords" (Mode-Conditioning Patch Cord) are required for the transmitter ports of LNW37, LNW49, and LNW50 circuit packs. Mode-Conditioning Patch Cords take the transmitter port output from the single-mode fiber and couple it to the multi-mode fiber core at an offset. This offset launch into the MMF minimizes differential mode delay and modal dispersion. With the use of Mode-Conditioning patch cords, transmission distances of up to 300 meters are allowed. See Figure 10-1, Transmission over multi-mode fiber connection using single-mode fiber offset-launch mode-conditioning patch cord.

With improved, recently introduced MMF specified to exceed 1 GbE fiber standards, transmission distances of up to 300 meters are allowed without the use of Mode-Conditioning patch cords. Several manufacturers offer this improved MMF (see the table below). These fibers, or their equivalents, do not require Mode-Conditioning patch cords when used with the LNW37, LNW49, and LNW50 circuit pack codes.

Table 10-78: MMF types that do not require mode-conditioning patch cords

Manufacturer	Product Name	Core Size
OFS Fitel	GigaGuide 62.5	62.5 mm
OFS Fitel	GigaGuide 62.5 XL	62.5 mm
Corning	InfiniCor CL 1000	62.5 mm
Draka Comteq	HiCap 62.5 mm	62.5 mm

Per usual practice, one must adhere to Alcatel-Lucent's receiver overload and sensitivity specifications for the circuit pack codes listed above. Multimode attenuators may be needed at the LGX.