The question is asked why it is sometimes necessary to use fiber optic cable instead of using copper wire cable. Fiber optic cable has benefits if any of the following characteristics are needed: security, lower weight, long distance communications and increased data transfer speed. Noise immunity to electromagnetic interference (EMI) is crucial in applications where there is high radiated electronic noise such as motors and high current switching environments. Even though standard CAT 5 copper cable has twisted pairs and some cables are shielded, in high electronic noise situations, the transmitted data can be corrupted. This problem at best causes data retries, which slows the overall throughput. As fiber optic cable is immune to noise, it is ideal for use in high noise environments. Securing transmitted and received data is the second benefit for fiber optic usage. Copper Ethernet cables radiate a small signal that can be intercepted and decoded without disturbing the integrity of the cable medium. As fiber optic does not give off any electronic radiation, the only way to intercept the data is to cut the cable and physically insert a tap. The interruption of data to insert a tap can be detected and investigated. The third benefit for fiber optics is due to its low weight. Fiber optic cable is approximately 8 times lighter than the equivalent length of CAT 5 cable. Large Aircraft is a good example of the need to lower weight. A commercial aircraft like a Boeing 787 can have 60 to 70 miles of cables. Not all the cables can be replaced by fiber optics, but the move to lower weight equates to better fuel economy and flight range. The fourth advantage is that Ethernet over fiber optic cable can operate at least three times the distance as copper CAT 5 cable (62.5 µm core OM1 fiber), or five times the distance using 50 µm core OM2 fiber. The last advantage / application for fiber optics is the speed of data transfers. To maintain existing network compatibility, the E4 has 1 Gigabit operation (the same as the VersaLogic wire Ethernet module MPEe-E3E). Note, there are faster Ethernet standards available; 10, 25, 50, and 100 Gigabit which are typically implemented using fiber optic links. The move to faster Ethernet standards requires more expensive controllers and hubs. It is not possible to implement a 10 Gigabit Ethernet on a Mini PCIe module due to the number of PCIe lanes required to interface with the controller chips. To be fair, the disadvantages of using fiber optics are higher cost and additional installation considerations. The cost of fiber optic installations can be approximately 35% higher than the CAT 5 wired cable. This cost includes the cost of the transceivers as well as cable termination costs. For short cable runs there is little cost difference, but for longer distances, fiber can be more expensive. The other potential disadvantage is routing: Fiber optic cable must have a minimum bend radius of one inch in diameter (it can be more depending on the cable). Bends of less than the one inch will result in a break in the fiber that must be replaced. There is also the issue of potential fiber compression where the jacket around the cable shrinks over time and causes internal ripples in the fiber that reduce the signal level at the output end of the cable. The use of preconditioned cables and service loops help to mitigate this issue.