Fiber optic proximity sensors used to detect the proximity of target objects. Light is supplied and returned via glass fiber optic cables.  Fiber optic cables can fit in small spaces, are not susceptible to electrical noise, and exhibit no danger of sparking or shorting. Light is supplied and returned via glass fiber optic cables.  Glass fiber exhibits very good optical qualities and typically carries high temperature ratings.  Plastic fiber can be cut to length in the field and can be flexible enough to accommodate various routing configurations.

Important parameters to consider when specifying fiber optic proximity sensors include detecting range, position measurement window, minimum detectable object, and response time.  The detecting range is the range of sensor detection.  For presence sensors, this goes up to the maximum distance for which the signal is stable.  For position measurement sensors, this is the distance range over which the position vs. output response is linear and stable.  The position measurement window is the width of linear region for the sensor.  For example, if the sensor could measure between 14 and 24 cm, this window would be 10 cm.  The minimum detectable object is the smallest sized object detectable by the sensor.  The response time is the time from target object entering detection zone to the production of the detection signal.

Choices for optical types for proximity sensors, fiber optic include through beam, retroreflective, polarized retroreflective, diffuse, divergent, convergent, fixed field background suppression, and adjustable field background suppression.  Through beam (or opposed mode) sensors incorporate a transmitter and a receiver on opposite sides of the target and evaluate absence or presence based on transmittance or blockage of the beam respectively.  Retroreflective sensors incorporate the emitter and detector in one body with parallel beams; a reflector opposite the target path is used to reflect the emitted beam back to detector; presence is detected when reflected beam is interrupted by an opaque object.  Polarized retroreflective sensors are a variant of the retroreflective in which the emitter and receiver have polarizing filters 90° apart, thereby making the reflector the only recognizable source.  With a diffuse sensor presence is detected when any portion of the diffuse reflected signal bounces back from the detected object.  Divergent beam sensors are short-range diffuse-type sensors without any collimating lenses.   Convergent, fixed focus, or fixed distance optics (such as lenses) are used to focus the emitter beam at a fixed distance from the sensor.  Fixed-field sensors are designed to have a distance limit beyond which they will not detect objects, no matter how reflective.  Adjustable field sensors utilize a cutoff distance beyond which a target will not be detected, even if it is more reflective than the target.  Some photoelectric sensors can be set for multiple different optical sensing modes.  Reflective properties of the target and environment are important considerations in the choice and use of photoelectric sensors.

Common configuration features for photoelectric sensors include beam visibility, light-on or dark-on modes, light and dark programmability, adjustable sensitivity, self-teaching, and laser source.  The body style of the sensor can be threaded barrel, cylindrical, limit switch, rectangular, slot, ring, and window or frame.  The sensor may be self-contained and may have a remote head.

Other important parameters to consider include output options, dimensions, electrical connections, and environmental operating conditions.