The Function Of Mode Conditioning Patch Cables

Posted on by FS.COM

A mode conditioning patch cord is needed at each transmitter/receiver when using multimode 62.5/125μm optical fiber for transmitting Gigabit data over distances greater than 300 metres.  Mode conditioning fiber patch cables, also known as Gigabit Launch Patch cord, which are used to adjust the outputs of singlemode Gigabit Ethernet transceivers to multimode cable networks. They are designed for Gigabit Ethernet multimode applications at 1300nm wavelength, are used specifically in Gigabit Ethernet 1000BASE-LX (and 1000Base-LH) applications where the objective is deploying new high-speed 1000BASE-LX routers, switches, or transceivers within existing multimode system backbones. These cables can be applied in Local Area Networks and Metropolitan Area Systems.

Why Mode Conditioning Cable Is Needed?

The Gigabit Ethernet application standard requires the use of fiber optic light to achieve the specified data transmitting rates. Usually people use long wave transceiver modules for Gigabit Ethernet, these modules have to operate both single mode and multi mode fibers. And as we know, multimode fiber manufacturing techniques create index of refraction anomalies along the centerline of the multi mode fiber core. When a singlemode laser is launched into the centre of a multimode fiber it may cause differential mode delay (DMD) results in reduced bandwidth over distance.

The Mode Conditioning Patch cord overcomes this problem by launching the laser light from the transmitter into a single mode fiber which is aligned with a precise offset from the centre of the core of a 62.5/125μm fiber. The light is launched about the multi-mode fiber at a precise angle, giving the cable its mode conditioning properties. The output of the patch cord is then compliant with the IEEE 802.3z standard for 1000Base-LX. Any attempt to connect 1000Base-LX/LH equipment over short distances of multimode fiber without the use of mode conditioning fiber will result in a high bit error rate, and eventually damage to the device. The launch of the light taken from the apparatus begins on a single mode fiber. The single mode fiber is precision blend spliced to the multi-mode fiber to a precise core positioning. The light is launched about the multi-mode fiber at a precise angle, giving the cable its mode conditioning properties.

How To Use Mode Conditioning Cables?

The mode conditioning patch cords are often used in pairs. That means you will require a mode conditioning patch cord at each end to plug the apparatus to the cable plant. When using mode conditioning fiber optic patch cords, we need to connect the yellow leg which is the color of single mode to connect the transmit side of the equipment (single mode Gigabit transceiver) while we connect the orange leg which is the color of multimode to the receive side.

Mode conditioning fiber optic jumpers are used in the 1300nm or 1310nm optical wavelength window, and should not be used for 850nm short wavelength window such as 1000Base-SX. All mode conditioning fiber optic patch cords are made with Duplex multimode fiber optic cable; with a single mode to multimode offset fiber connection part in one of the two legs. Mode Conditioning Cables are needed in applications where new high-speed Gigabit 1000BASE-LX routers and switches are being deployed into existing multimode plants.

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