For those who haven't read "Flash Boys", this a synopsis of the book:
Canadian banker Brad Katsuyama notices prices for stocks he is buying change price almost the instant he places his order to purchase them.
Turns out that this happens when he places a larger order than can be filled at a single exchange. After some investigation he determines that HFT traders "see" his trade on the local NJ exchange and buy up stock at other (further away) exchanges before said banker can fill his order at the original (lower) price.
His solution: Send orders to multiple exchanges but delay the orders to the closest ones so orders arrive at exchanges more or less simultaneously thus defeating that particular HFT strategy. The coil of fiber is the method used to achieve that delay.