Hackaday Prize Entry: An Optical Power Meter

This is the type of crowd that’s famous for building their own test equipment. If you need a way to program a flash chip, don’t go out and buy one — you can just build one. Need a spectrum analyzer? You can build that out of copper clad board. For his Hackaday Prize entry, [oakkar7] is building an optical power meter, capable enough to do futzy fiber work, but still completely DIY.

When you get into networking and telecom connections that don’t begin with the letters ‘RJ’, you start to stumble upon SPF transceivers. These ‘small form factor pluggable’ devices are little modular transceivers capable of handling fiber, Gigabit Ethernet, and other slightly weirder bit pipes. When used with fiber, they can measure optical power in dBm and watts, and can be debugged by a UART.

[oakkar]’s optical power meter uses these SPF transceivers, tied together with a fairly simple circuit consisting of an Arduino, a few tact switches, a Nokia LCD, and an FTDI UART. The key in tying all of this together is an Arduino library for SPF and DDM (Digital Diagnostics Monitoring), giving the user access to all the configuration bits in these transceivers.

While the circuit is simple enough to be built on a piece of perfboard, [oakkar] really knocked it out of the park with the enclosure on this one. With just a little bit of laser cut acrylic and a few standoffs, [oakkar] has a device that actually looks professional, and has most of the capabilities of fancier, more expensive tools.

25 thoughts on “Hackaday Prize Entry: An Optical Power Meter

          1. It’s not just blue, although our eyes are more sensitive that way. But it’s also not just LEDs either. I find some of the newer headlights rather uncomfortable to look at.

          2. Yep, an old nokia I inherited from a friend temporarly blinded me. I had taken off the case, as it was dirty and broken, and I was playing a game of snake when I began to see blind spots growing in my vision.

  1. I’m gonna be that pedantic asshole today and point out that SFPs don’t use UART for management, they use I2C (or “two wire serial port interface” because Philips was jerks until the mid ’00s).

  2. Oh nice. I did this a couple years ago at work. I have a pair of testers that modulate the light to send data, so if there is a link the remote end gets a signal containing the power from the other tester. So at both ends the screen shows the RX power at both ends :)
    No buttons other than on/off on mine and they wirelessly charge too.

  3. Thanks all for interest.

    Like ScriptGiddy says: it is SFP, not SPF.

    And the case is not laser-cut. It is cut by hand scroll saw.

    For safety, my SPF module (most module >= 10km range) uses Class-1 laser. So, it is safe to handle in normal condition. There are various range/speed/type of SFP modules (like long haul DWDM modules) may use different class and output powers level. So, take care your own.

    For BLUE LEDs SUCK: Thanks for your shared infos. Actually, I also feel inconvenience of looking LEDs brightness. I will replace normal LEDs and adjust series resistors. For nokia lcd, I cannot replace the back light LED. I may add back light adjustment with PWM for it.

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