Things to know when using mode conditioning cables to patch an existing multimode cable plant to your Gigabit LX equipment.
1) Mode conditioning cable are normally used in pairs. That means that you will need a MC cable at each end to connect the equipment to the cable plant. So then these cables are usually ordered in even numbers. The usual reason why someone may order one cable is so they may keep it as a spare.
2) If your gigabit LX switch is equipped with SC or LC connectors, please be sure to connect the yellow leg (Singlemode) of the cable to the transmit side, and the orange leg (multimode) to the receive side of the equipment. It is imperative that this configuration be maintained on both ends. The swap of transmit and receive can only be done at the cable plant side. (see diagram below)
3) Please see Frequently asked questions below for additional important information.
Principals and Basics on how a Mode Conditioning Cable works
The launch of the light coming out of the equipment begins on a Singlemode fiber . The Singlemode fiber is precision fusion spliced to the multimode fiber to a precise core alignment (see fig. 1). The light is launched on to the multimode fiber at a precise angle, giving the cable its mode conditioning properties . Looking at the mode conditioning cable assembly in figure 2, we can see that the fusion splice this protected by a black over-wrap. notice that on the right side there is an orange and a yellow cable. This is the side of the cable that connects to the gigabit equipment with the yellow Singlemode leg connecting to the transmit side .
Frequently Asked Questions
The great demand for increased bandwidth has prompted the release of the 802.3z standard (IEEE) for Gigabit Ethernet over optical fiber. 1000Base-LX requires the use of a launch conditioning patch cord to allow for proper propagation of the laser VCSEL light along the multimode fiber.
|How do I run Gigabit Ethernet (LX) over my existing multimode fiber optic cable plant?
||Use a Mode Conditioning Cable.
|Is there a distance cutoff to where mode conditioning is not required?
||Generally, Mode Conditioning patch cords are required for link distances greater than 984 feet (300 meters). We have heard some case stories where that distance has been lesser or greater. To our experience, the distance of 984 feet (300 meters) is just a benchmark. Your results may vary according to various different equipment and field conditions.
|What is the stock and availability situation with mode conditioning patch cables?
||All of our mode conditioning cables are custom made to order . By industry standards, our lead times are very short . The lead time will vary according to the quantity desired , and the production load at the time of the order. Average lead times are as follows:
1 - 2 days for orders of 1 to 12 cables,
3 - 5 days for orders of 12 to 40 cables,
1 week for orders of 40 to 100+ cables.
Note: MT-RJ and MU cables may have higher lead times.
|Where can I find an equivalent to the CAB-GELX-625= for my Cisco Gigabit Network Equipment?
||Our 3 meter SC to SC Mode Conditioning patch cable is 100% compatible with the CAB-GELX-625= cable as specified Cisco for their Gigabit equipment, including the Catalyst family.
|Do all multimode fiber types require mode conditioning?
||Some manufacturers of the newer "high end" multimode fibers claim that that their premium line cables will not require mode conditioning. Contact the manufacturer of your installed cable for the answer.
|When I hold the yellow Singlemode cable up to a light, the light does not come through on the other side. Does this indicate that I have a defective cable?
||The core of the Singlemode cable is so small than it does not gather enough light for it to be visible without a microscope on the other side. this is a normal condition for any Singlemode cable .
|Can I use a mode conditioning cable to convert Singlemode to multimode or visa-versa?
||No. Conversions of multimode and Singlemode require Media Converters.
The Mode Conditioning Patch Cord is designed for long wave (-LX) multimode applications of Gigabit Ethernet. It is compliant with this IEEE 802.3z application standard. This patch cord consists of duplex SC connectors on each end of a cable assembly with a single-mode fiber offset to a multimode fiber connection point in between.
The need for this patch cord is due to the single-mode launch nature of the -LX or long-wave (1300 nm) transceiver modules used for Gigabit Ethernet. These modules have to operate for both single-mode and multimode fibers. Launching a single-mode laser into the center of a multimode fiber can cause multiple signals to be generated that confuse the receiver at the other end of the fiber. These multiple signals, caused by Differential Mode Delay (DMD) effects, severely limit the cable distance lengths for operating Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by allowing the single-mode launch to be offset away from the center of a multimode fiber. This offset point creates a launch that is similar to typical multimode LED launches.
- IEEE-802.3z (Gigabit Ethernet) Compliant
- Permanent offset closure
- Low profile offset closure
- Low loss
- Fits existing cabling scheme
- Easy to use
- "Masks" Differential Mode Delay (DMD) effects
- Correct offset always maintained
- Aesthetically pleasing
- Uses precision ceramic ferrules
- Use in place of standard equipment-to-cable plant patch cord
- Functions the same as a standard patch cord
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|Disclaimer: We have provided this article as general installation advice to our customers. We make no claims about the completeness or the accuracy of the information as it may apply to an infinite amount of field conditions. It is the responsibility of the person or persons using this information to check with all concerned parties, owners and local authorities, etc. before doing an installation. Users of this information agree to hold Atcom Inc. harmless form liabilities of any kind relating to the use of this information.
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