The many ‘modes’ of multimode

Fiber types are differentiated as multimode or single mode. Single mode was always easy for me to understand but I could never quite understand what ‘multimode’ actually meant. I’m written some notes for myself on this topic that I thought I’d share. I’m sure some physicists will have an allergic reaction to my take, but I’m happy to pay that price to learn a little more.

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Hardware – Equalization and Pre-emphasis

Screen Shot 2014-02-09 at 9.39.58 AMBefore we look at equalization and pre-emphasis, we should examine some fundamentals of waves and signals. A perfect square wave is a really useful way of representing a waveform in the time-domain, but it’s not the only way of looking at the signal.The name ‘time-domain’ may be new but the view is familiar to us all, you have amplitude on the vertical axis and time you have time on the horizontal scale.

Ideal square waves need infinite bandwidth

The square wave is easy to understand, but unfortunately the ‘perfect’ square wave is a purely theoretical construct. A square wave is actually constructed of many sine waves of different frequencies and amplitudes added together [1]. The fundamental frequency of the signal (e.g. 10Khz) is a sine wave and has the highest amplitude. However there are other many other frequencies called harmonics, which must be successfully received and added to the fundamental signal to ‘square out’ the waveform. To view these signals we need to switch to a new view, the ‘frequency-domain’.  Continue reading

Video – 10G Fiber Transceivers – Network Sherpa

I’ve just recorded a quick video about 10Gbps fiber transceivers, There’s a first for everything I guess.  It’s a cheat sheet which describes the different transceivers, where they’re commonly found and the connectors you use.

I’d love to hear your take on the video.  Too long… too short, music too cheesy (yeah I know!), etc.   All constructive feedback is welcomed.