GPS is a revolutionary piece of communications technology that provides us with the means to determine our exact location more or less anywhere on earth. It also provides a highly-accurate timing signal that is used to synchronise communications networks worldwide.
However, satellite signals cannot usually reach indoor locations because of the blocking effect of the building structure.
A GPS repeater system is used to bring satellite signals indoors, but sometimes the distance from outdoor antenna to indoor repeater unit is too great and exceeds the practical limitations of even the best low-loss coaxial cable.
Thankfully, GPS-over-fibre is a practical solution for distributing GPS signals to the far reaches of a building interior.
We are going to take a look at what GPS over fibre is as well as the benefits this technology brings.
GPS over fibre offers a solution to weak, or non-existent, indoor GPS signals by extending the distance between the GPS antenna and the repeater/receiver, up to several kilometres if required. This allows for a greatly improved GPS signal strength in areas that would not normally have been able to receive it.
A GPS receiving antenna is placed outside the building, preferably at roof level, where it has a clear view of the sky to ensure it can receive a signal from as many satellites as possible.
A coaxial cable connects the antenna to an optical transmitter (TX) module inside the building.
The purpose of the transmitter module is to convert the RF signal into light by using a laser light source, which is then carried via a fibre optic cable to an optical receiver (RX) module.
The receiver module then converts the light signal back into an RF signal, amplifies it and impedance matches it to the GPS repeater/receiver.
– Low signal loss allows for connections across great distances
– Optical fibre is immune to electromagnetic and radio frequency interference
– Easy installation – fibre is thin and lightweight compared to some coaxial cables
– Cost-effective solution – fibre optic cable usually costs less than coaxial cable
GPS over fibre opens up a world of possibilities for providing GPS signal in areas it could not previously reach. This affordable technology is paving the way in the distribution of indoor GPS signal over large distances.
It can be used to connect an outdoor antenna to a GPS repeater system, which re-radiates signal inside a large area for multiple receivers to use. Or the antenna can be connected by fibre optic cable to a Network Time Protocol (NTP) server in a data centre.
This case study shows how a GPS over fibre link provides an accurate timing signal inside an earthquake monitoring system deep under the Austrian Alps.
If you are interested in using GPS over fibre and would like to know more, our team at FalTech offer the best advice and solutions available. Contact us today to discuss your requirements further.
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