Why optical cabling on farms?
This is a primer on the usefulness of fiber optic cabling for data transmissions on farms. I had meant to have a session on this at the 2024 GOAT but things went a different way. It may be that your needs are perfectly met by having a single cheap router hanging in the window or that may not be enough, that is up for you to decide.
This isn’t professional advice but the ramblings of an old man on a farm too stubborn to use grammarly or chatgpt. Your mileage may vary.
As always, exercise caution when working with machinery and remember that Mr. Volt and Mr Ampère are not always your friend. Being made of glass or plastic, fiber does not conduct electricity which is helpful from a few points of view:
1) Ground loops
It’s not unusual for grounds to have large (>50V) voltage differentials in between circuits within and without buildings, even if they are being fed from the same transformer. This can occur in all installations, even those maintained by conscientious electricians, and will worsen as both ends of the transmission cable get further apart.
This is a serious hazard if you are hooking up telecommunication equipment as the cable ground will be shorting two pieces of equipment at different electrical potentials. Fiber optic cabling does not conduct electricity at all which mitigates this problem.
Some smart-aleck in the back of the room is going to point out the benefits of differential signalling and separating cable shield (mechanical) ground from the signal (equipment) ground. Similarly to household light bulbs vs. farm-service light bulbs, there are different grades of telecommunications equipment that implement different levels of isolation and the market sometimes fails to differentiate between them: Caveat Emptor.
I’ve personally seen a computer turn itself into a toaster oven because of a ground loop on an industrial telecommunication line and that was with equipment that was supposed to be electrically isolated!
2) Lightning safety
Farms have large open areas with tall structures like barns, houses and water towers that are attractive grounding paths for lightning. Running conductors can be tricky in that they can pass unsafe currents from one structure to another, even through the building that receives the strike may itself be unaffected.
Various models of lightning arrestors and surge protectors are available to mitigate this with different degrees of protection and service lifetimes. Be aware that many models of arrestors will destroy themselves (by design) during a lightning event. This protects the equipment at the cost of replacing the arrestor and the equipment downtime. Anecdotally, I’ve had to replace one manufacturer’s ethernet lightning arrestor three times in the past two years while another installation from a second manufacturer has yet to fail. These were small scale storms, but even a high quality arrestor can only do so much with a direct lightning strike in a major storm.
Electrical fencing, conductive wire strung over long distances and deliberately insulated from the ground, creates an effective path for lightning to travel horizontally with, even during near misses. Your fence energizer must be installed with this in mind in order to shunt the lightning energy to the local ground during a lightning event. The issue is that this causes a brief but significant ground loop current that can spread to data lines and local power supplies.
Of course lightning can cause damage without having a direct path for the current to follow: a transient high-voltage and high-current event, lightning is also a plasma and electromagnetic pulse phenomena. This means that it can damage electronics by inducing currents into circuits even if no current path exists. Putting farm sensors and electronics into grounded metal enclosures can mitigate this as the enclosure behaves as a faraday cage, protecting the enclosed circuits.
Fiber optic cannot transmit electrical current and while a direct lightning hit will physically damage the fiber it is unlikely that any induced light pulse will be coherent enough to travel down the line and damage the fibre transceivers or the rest of the equipment. It is an ideal means of electrically isolating a piece of equipment that is at high-risk of being affected by lightning or that needs to operate in an environment unsafe to electricity, such as wells.
3) Better performance over long distances
Distance is another aspect of fiber performance that is attractive for farms that have to transmit data over longer stretches. 10base-t ethernet has a limitation of about 300FT, low-speed serial line drivers and point to point wireless (line-of-sight and antenna height permitting) systems can both achieve several miles. Wide area WIFI is also possible if deploying a network of access points is possible.
Air line is an option when placing cable on a farm. It is three times cheaper than direct burial in the best of scenarios and existing electrical power poles can be used (subject to pole ownership and safety standards). At issue is that poles are not always in the desired locations and oversized farm equipment seems to have a knack for reaching cabling previously thought to be unreachable.
From a cabling cost perspective, direct burial (lightly) armoured ethernet cabling is roughly half the cost of fibre, it is also significantly heavier and costs increase linearly with each new ethernet cable. By contrast, the cost of adding a strand to a fiber cable assembly is negligible which means that the marginal cost of adding more capacity at burial time is also negligible. The benefit of having multiple relatively low cost fiber paths is that multiple systems can have their own physical fiber without having to invest into costly multiplexers, delving into byzantine protocol converters (older telephone systems) or maintaining separate physical networks for contractual reasons.
Power is a consideration in that most other data transmission technologies require repeaters at set intervals or hefty power supplies to overcome long distance transmissions. OM2 fiber will reliably transmit Gigabit ethernet over a quarter of a mile using affordable LED-driven transceivers which would normally require a parabolic antenna and 10 times the power consumption. In terms of power utilization and bandwidth, fiber is a strong choice for communication with field equipment since even battery-powered end devices can be deployed.
4) MOAR! Bandwidth
Fiber advocate like to boast of how much bandwidth is available and often over-focus over big numbers rather than explaining what are the possible applications of having such a transmission medium available. The combination of low-power, high-bandwidth and electrical isolation means increased safety and convenience for farm installations.
It is common for farm houses to have tall tv antennas and larger satellite dishes for television access. These have often been installed close to the home because of cabling even through they can attract lightning, may suffer from line-of-sight issues and be an eye-sore. Commercially available emitters will convert an entire OTA TV or Satellite dish signal over a single fibre while incurring minimal loss and facilitating signal splitting over multiple receivers. This means that the entire “antenna farm” can be relocated away from the dwelling with no loss in the quality of service.
Other farm applications have been under-served bandwidth-wise, such as barn monitoring during foaling season or of sick animals. Closed circuit television monitoring does not need to be a grainy, out-of-focus black and white image. High definition 1024p cameras are now available at reasonable prices. Not because you a filming a motion picture but rather because you are trying to monitor the subtle behaviour of an animal without guessing at a screen.
Lastly, a reliable internet connection and a computer are now a requirement in the maintenance shed. Farming implements are being rapidly fitted with their own network of computers, we have to consult online manuals for the maintenance of equipment, to reorder parts and get expert guidance on minutiae that would we could not have fathomed a few years ago.
In the next post I will review some issue in fiber (and cabling) burial in farm settings.
