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Pepperl+Fuchs Blog

6 Steps to Selecting a Fiber Optic Cable

Posted by Zach Steck on Wed, Mar 19, 2014

When selecting a fiber-optic cable, it is not as simple as “What fiber cable goes with this sensor?”  There are multiple factors that contribute to selecting the appropriate fiber-optic cable for your application. 

6 Steps to Selecting Fiber Optic CablesLet’s take a look at each step to help you narrow down exactly what you need.

Step 1: What fiber-optic sensor will I be using?

Each fiber-optic sensor has a select group of fiber-optic cables that are compatible for that model.  Our catalog does a good job breaking up these cables into groups based on the sensors they work with.  For the most part, there are sensors that are designed for plastic cables and there are sensors designed for glass cables.  We also have some sensors that are usable with both or with an additional adapter.

Step 2: Diffuse or thru-beam?

Fiber-optic cables are available that operate in one of these two functions:

  • Diffuse cables have one sensing head with two leads going back to the sensor for the emitter and receiver.  These are short range but do not need anything mounted across from them to detect a target.
  • Thru-beam cables have two separate sensing heads that are mounted across from each other and trigger an output when the beam is broken.  For this setup, you would need two pieces of the same cable that  run back to the emitter/receiver of the sensor.  Plastic thru-beam fiber-optic cables are sold as a pair, while glass cables are purchased individually.  Thru-beam cables will get you a longer range, and specialty heads are also available (slot type).

Step 3: Head Type?

There are various head options for fiber-optic cables to assist in mounting within the application. These include:

  • Straight smooth cylindrical
  • Straight threaded cylindrical
  • Side-view/Periscope
  • Rectangular
  • Specialty (slot, bendable probe, array, etc.)

Step 4: Cable type and sheathing?

As mentioned earlier, there are two types of fiber-optic cables: plastic and glass. There are also several options for cable sheathing including:

  • PVC
  • PE (polyethylene)
  • Stainless steel (armored)
  • Silicone
  • PTFE (Teflon)
  • Fluorine

The sheathing option will contribute to the usable temperature range and bending radius of the fiber-optic cable.  Some are offered for specific applications such as PTFE and fluorine, which are chemically resistant in fluid level indication.

Step 5: Sensing range?

Sensing range for a fiber-optic cable is determined by the combination of the sensor and fiber cable selected. Some fiber-optic sensors are capable of various modes that will affect the range. The effective range is displayed in our catalog by sensor model and mode (if applicable). See the example below:

Sensing range for fiber optic cable

Step 6: Fiber-optic cable length?

The length of the fiber optic cable needed to reach the fiber optic sensor.  Lengths vary from 3 feet to 10 meters (~30 feet).

Using the 6-step approach, let's look at a quick example. Suppose you need a cable with the following characteristics, based on your answers to the 6 questions:

  1. Used with the SU18 fiber-optic sensor
  2. Thru-beam operation
  3. Threaded cylindrical head
  4. Stainless steel sheathing
  5. Minimum 500 mm range
  6. Short length, 3 foot maximum

The best option based on the answers to the 6 steps above would be model LME00-1.0-1.0-K151:

Glass fiber optic cable

Free Download: Photoelectric  Fiber Optic Sensors and Cables

Topics: Cables/ Cordsets, Photoelectric Sensors

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