# Fiber Optics Synchronization tunable delay

Discussion in 'Homework Help' started by cl10Greg, Nov 14, 2014.

1. ### cl10Greg Thread Starter Active Member

Jan 28, 2010
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Hello Everyone,

I am working on a homework problem that I have attached below that is based out of Optical Networks: A practical approach 3rd edition. So the outcome needs to be an algorithm to represent the tunable delay.

So the way I am picturing it is that there is two signals that both have period T that are out of synchronization by z. So I need to find a formula to represent z to align the two signals. The 2x2 switch can either be cross state (c = 0, adds delay) or a bar state (c=1, no delay). Each delay is in steps of T/2^k-1.

So from a logic point of view I am picturing a feedback system to tune in the delay.
• Find the starting value of z (signal 1 - signal 2)
• signal goes through crossed 2x2 switch (c1 = 0)
• Find new z after delay (signal 1 - signal 2)
• If z > 0 +- tolerance
• ci = 0
• calculate new z
• Repeat until z is within a tolerance of 0 so the signals are now aligned
• Count the amount of repetitions to determine the number of stages to make this happen.
This is course tuning (I don't need fine) but I need a way or some guidance on if my thinking is correct and how to correlate that to a algorithm. Also, what is the point of the bar state if I am most likely never going to use a pass through of the switch? I guess if the delay went past the synchronization point but then I would have to tune the other signal but really we're only manipulating the one signal to match the reference signal. Any thoughts or help is appreciated.

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