Introduction to Passive Optical Components: Optical Circulator, Isolator and FBG Sensor
Home WDM & FTTX Introduction to Passive Optical Components: Optical Circulator, Isolator and FBG Sensor

Introduction to Passive Optical Components: Optical Circulator, Isolator and FBG Sensor

Posted on by FS.COM

Nowadays, passive optical network(PON) is widely used by people as a promising solution for modern access telecommunication networks. Applications of passive optical networks, especially the WDM-PON, plays an important role in FTTx deployment solutions. With the developing of technology, we need more creative and cost-effective PON systems which are no longer limited by the basic elements. Besides those basic elements, engineers have contributed to the evolution of optical communication by designing some innovative passive devices to improve functionalities, reliability, and economical efficiency of optical networks. About the word “passive”, here refers to those devices do not require electrical-to-optical or optical-to-electrical conversion during its operation. In general, the common passive optical components include simple fiber optic connectors, splices, couplers/splitters and fixed fiber optic attenuators. Moreover, optical devices like switches, variable optical attenuators, circulators, isolators and FBG(Fiber Bragg grating) sensors are also widely used in a PON network structure. This paper will focus on description of optical circulators, isolators and FBG sensors.


Optical Circulators
A optical circulator is usually a three-port circle device designed serving as optical one-way streets so that light entering any port exits from the next. In other words, direct light from port 1 to port 2, port 2 to port 3, with none going 2 to 1. But now there are other options, such as 4 ports(has one additional bi-directional port), 1×2 ports, 2×2 ports types in the market as the technology improves. A optical circulator can be used to de-couple transmitted and received signals traveling along the same fiber(in short, the bi-directional transmission), as a type of branching component that distributes/isolates optical power among optic fibers, based on the direction of the lightwave propagation. The principle of optical circulators is using the Faraday rotators.


  • Low Back Reflection
  • High Extinction Ratio
  • Low Insertion Loss
  • High Return Loss
  • Excellent environmental stability and reliability


  • DWDM system
  • Add-Drop Multiplexing
  • Fiber Amplifier
  • Fiber Sensor
  • Chromatic Dispersion Compensation Devices
  • Fiber Bragg Grating
  • Polarization maintaining optical system


Optical Isolators
A optical isolator operates in a similar way to a optical circulator, except that the reverse propagating lightwave is lost instead of being directed to a third port for output. A optical isolator is a two-port passive component which transmits light with low attenuation in only one direction. optical isolators’ main function is to reduce or eliminate back reflection and controlling noise. In general, optical isolators are used as both integral and in-line components laser diode modules and optical amplifiers, and to reduce noise caused by multi-path reflection in highbit-rate and analog transmission systems. The working principle of optical isolators is based on Polarizers and Faraday Rotators.


  • Low insertion loss
  • Low Extinction Ratio & High Isolation
  • High stability and reliability
  • Good uniformity


  • EDFA
  • Fiber sensor
  • Fiber Optical Instrument


FBG(Fiber Bragg grating) Sensors
FBG(Fiber Bragg grating) is a passive and discrete optical component at a specific spot in an optical fiber which reflects light of a specific wavelength and is present within the core of an optical fiber waveguide. FBGs are now increasingly being used in sensing applications and are enjoying widespread acceptance and use. The common types of FBG sensors include temperature FBG sensor, weldable FBG strain gauge sensor, displacement FBG sensor, acceleration FBG sensor, pressure FBG sensor and so on. Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, FBG sensors are becoming a mainstream sensing technology.
FBG sensor


  • Immunity to electromagnetic interference
  • Good passive nature
  • Small size
  • Fast response
  • High stability and reliability
  • Extensive available range for measure physical parameters


  • Civil engineering
  • Bridge monitoring
  • Structural health monitoring
  • Water level remote measurement
  • Strain monitoring of concrete beam


Passive Optical Components in Fiberstroe
Fiberstore is always specialized in optical communication products, certainly including the fiber optic passive components. Passive Optical Components, including optical isolators, optical circulators, fiber collimators, and optical attenuators are all offered in Fiberstore with highly quality and reasonable prices. Additionally, we welcome any custom requirement in various parameter designs, such as beam spot diameter, working distance, dimension etc.

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