Mode Conditioning Fiber Optic Patchcords

Mode Conditioning Patchcords are a duplex multimode cord that has a small length of singlemode fiber at the start of the transmission leg. These are tested utilizing the industries latest equipment for superior quality. Mode Conditioning Patchcords are assembled with connectors using 62.5/125um or 50/125um fiber.

 
Gigabit Ethernet (GbE) describes a Local Area Network capable of sending and receiving over one gigabit (1,000,000,000 bits) of information every second. Transmitting connectionat high speed requires a laser light source instead of an LED source to power the network. This is because the operational limit of LED's is about 620 million bits per second. Due to the lasers faster rise and fall times, the pulses of light injected into the fiber are more tightly packed together thus greater bandwidth. GbE marks the first wide spread use of lasers to launch light into multimode fiber.

 
When you inject laser light into multimode fiber only a portion of the core is filled due to the lasers small spot size. It was initially believed that this launch condition would naturally increase bandwidth in multimode fiber. The reasoning was that because the core is not completely full of light there would be empty modes in the core and a lesser chance of modal dispersion occurring. However, test on high-speed networks showed that this did not always occur.

 
Researchers soon discovered that the multimode fibers currently available have a "dip" in the center of their refractive index profile. When laser light is launched into this "dip", multiple signals can be generated that overlap each other and make it difficult for the receiver to interpret. This condition is known as Differential Modal Delay (DMD).

DMD can cause a multimode fiber with a laser source to have a lower bandwidth than the same fiber with a LED source. The way to control DMD is to find a way of steering the injected laser light around the "dip". That is the function and purpose of a Mode Conditioning Patchcord.

 
A Mode Conditioning Patchcord is a duplex multimode cord that has a small length of singlemode fiber at the start of the transmission leg. The basic principle behind the cord is that you launch your laser into the small section of single mode fiber. The other end of the singlemode fiber is coupled to multimode section of the cable with the core offset from the center of the multimode fiber. The laser light thus misses the "dip" and this new launch condition more closely mimics a standard LED launch. The bonus is that you still retain the speed advantages of using a laser.