How to Identify Alarm States on GPS over Fiber Modules

Sean Walker, ViaLite‘s customer support engineer, shows how to use the GPS mode on ViaLiteHD Blue OEM Modules, which allows the user to know when there is a fault in the system. If there is no current loading on the RF connector port, either due to no connection or a fault with the amplifier in the antenna, the transmitter switches off its laser, forcing an alarm condition at the receiver end.

Find out more about GPS/GNSS antenna loading and alarm states here.

Video Transcript

Hello my name’s Sean Walker, I’m customer support engineer for ViaLite. Today I’d just like to take you through our GPS antenna alarm system that we have in place for our Blue OEM modules.

So I’ve got two Blue OEMs here. I’ve got a Tx module which as you can see is displaying a red LED and I have an Rx module which is also displaying a red LED. So the device at the moment is not connected to our GPS antenna, so therefore the laser is disabled and obviously our receiver module doesn’t have a fiber coming to it, so it’s not receiving a signal. So it is also in alarm condition. So I’ve got my Blue OEMs powered up with the power supplies here and I’ve got my GPS antenna. This is a five volt GPS antenna and our Tx modules come with a five volt or a 12 volt version. So in this case we have the five volt antenna and we have our five volt Tx module. If you’re using a 12 volt antenna, then you need to be using our 12 volt version. So, what the system does is it looks for the loading of the GPS antenna on the system.

So as soon as you connect an active GPS antenna to the Tx module, the laser will become enabled, as it senses that loading from the antenna. So if I connect the antenna there, as you can see, we now have a green LED. So in order to complete the link, we need to connect our fiber in between. So we’re just going to connect the fiber up and as always, we’re going to give the fiber good clean before we connect it into the module. So using our cleaning cassette, we’ll give the fiber a clean and we’ll connect it directly into the module. And then with the other end we’re going to do the same for the Rx module. We’ll give it a clean and we’ll pop the fiber into the fiber port on the Rx module. And as you can see now we have a green LED on the Tx module and a green LED on the Rx module.

Now if you have a red LED on your Rx module, but your Tx module is green, then this indicates that there is an issue with the fiber connection between the Tx module and the Rx module. So check your fibers and check your ports and make sure that all of your fibers are clean. If you have a red LED appear on your Tx module, this normally indicates a fault with the GPS antenna.

So if the GPS antenna becomes faulty or if the coax gets damaged, which I’ll replicate here by removing the coax, as you’ll see, the LED now goes red into the alarm state. And subsequently because the laser is disabled, the receiver is also not receiving a light signal.

So this summarizes our alarm system for the GPS antenna modes. Hopefully that gives you all the information you need, but there is more information available on the website so please pop over to vialite.com to see more information there.