What people think fiber looks like V. Reality

This image or a similar one, are often what people picture when you ask them to imagine what a fiber optic cable looks like. While it looks good and flashy, in reality this cable would operate poorly and be nearly impossible to work on compared to an actual communications grade fiber optic cable.

This is the internal structure of an actual communications grade 120 count fiber optic cable. You can see the rainbow of colors used on the buffer tubes and the individual fibers they surround. This coloring system is a standard system used across the industry which aides in identifying specific fibers and where they go. Each colored buffer tube contains 12 individually colored fibers. The black bar in the middle is what is known as a strength member which is used to support the weight of the cable and increase its tensile strength.

This is a cross section of the cut cable. Looking directly into a fiber optic cable is extremely hazardous and I am only doing so here for demonstration purposes being that the cable is only a 4ft cut section. Looking in any fiber optic cable is hazardous in any situation, however the laser that would be used with this cable is rated as a Class 4 transmission laser which can cause skin damage and instantaneous blindness if mishandled. If you have fiber to your home the laser class should be much lower down to a Class 1 which is no more harmful than your DVD player unless you take it apart.

In this picture you can see the buffer tubes, the fibers, the strength member, and around the edges you can see small threads. These small threads are a mixture of fiberglass and Kevlar depending on the manufacturer of the cable. In this case the cable was made by Corning so the threads are Kevlar only.

Here is a close up of the orange buffer tube with my fingers for a size comparison.

This is the heart of the cable, these are the individual fibers that carry modulated light used to transmit information. The individual fibers shown here are used primarily for diplexed fiber setups (more on that later) so each neighborhood will use two of these to provide service to a handful up to 1500 cable customers. Each one of the individual fibers shown is a single mode fiber which has a core thickness of just 8-10 microns where as an average human hair is 0.07mm. This makes the fiber core 7-8 times smaller than a human hair. (EDIT: Thank you comments. I'm bad at math, post originally said 70 times)

There are a few different methods to transmit and receive information using light however i'm only going to touch on the two most common.

Method 1 splits the forward and return light onto its own fibers using an optical diplex filter. This is the preferred method as it allows the flow of information to be 100% continuous if it is required.

Method 2 uses a single fiber to transmit both streams of information in each direction. To do this, the transmitting laser at each end have to take turns. When side A is transmitting, side B has to turn off its transmission laser and turn on its optical receiver to capture the burst. When side B is transmitting, the process is reversed. This flip flopping of transmission happens a few thousand times per second.

Thank you for reading. Now here is a picture of a vicious dog. Thankfully I read the sign before I was ripped to shreds.