--- title: How Does a Dispersion Compensating Fiber Reduce Chromatic Dispersion? description: Learn more about chromatic dispersion and how a dispersion compensating fiber is used in fiber optic networks to mitigate this performance characteristic. image: https://www.m2optics.com/hubfs/images/Wavelength%20vs%20Refractive%20Index.gif --- - **Phone** [919-342-5619](tel:919-342-5619) - **Toll Free** [866-269-2902](tel:866-269-2902) - **Email** [sales@m2optics.com](mailto:sales@m2optics.com) [![footer-logo](https://www.m2optics.com/hs-fs/hubfs/M2_Optics_2021/footer-logo.png?width=166&height=58&name=footer-logo.png "footer-logo")](https://www.m2optics.com/) [![Request a Call](https://no-cache.hubspot.com/cta/default/39436/fc7235a3-fa4d-4c7f-bc75-7336bfb927cc.png)](https://cta-redirect.hubspot.com/cta/redirect/39436/fc7235a3-fa4d-4c7f-bc75-7336bfb927cc) # How Does a Dispersion Compensating Fiber Reduce Chromatic Dispersion? Posted by [George Zhu](https://www.m2optics.com/blog/author/george-zhu) on Thu, Apr 27, 2017 @ 16:04 PM - [Tweet](https://twitter.com/share) An important factor in the performance of fiber optic communications systems, **chromatic dispersion** is a topic and performance characteristic that is important to both understand and account for when operating and/or designing equipment for fiber-based networks. ** What is Chromatic Dispersion in Fiber Optics?** When shining a beam of white light into a prism, you see the light is composed of a rainbow band or light spectrum. This phenomenon is an example of [chromatic dispersion](https://www.m2optics.com/blog/bid/61431/chromatic-dispersion-in-optical-fibers). Red light with a wavelength of 700nm and violet with a wavelength of 400nm are at the two ends of the visible spectrum. But what causes the light with different wavelengths to separate from each other? It's the glass! Whether it is a prism made of glass, or an optical fiber with a fused silica glass core, they both have the ability to bend light with different wavelengths to different angles because glass is a type of dispersive media. To characterize glass or other types of media that light can travel, a parameter is used called *refractive index *(or also *index of refraction*). This number refers to the speed at which light propagates through a medium. The typical index of refraction for a single mode optical fiber is around 1.461, meaning that light travels 1.46 times faster in a vacuum than it does in a fiber. However, this value varies slightly at different wavelengths. Typically in optics, the longer the wavelength, the lower the refractive index (see Fig. 1 below).  ** ![Wavelength vs Refractive Index.gif](https://www.m2optics.com/hs-fs/hubfs/images/Wavelength%20vs%20Refractive%20Index.gif?width=207&height=262&name=Wavelength%20vs%20Refractive%20Index.gif)** **Figure 1:  Refractive Index vs. Wavelength2** The definition of the velocity of light is: *velocity = speed of light / refractive index* As a result, with different colors of the light spectrum travelling at different speeds due to the differences in refractive index, in the figure above red light travels faster than blue, due to its lower index. Over distance, red and blue will be further separated, thus the signal will be broadened: ![Pulse Broadnening Effect.gif](https://www.m2optics.com/hs-fs/hubfs/images/Pulse%20Broadnening%20Effect.gif?width=640&name=Pulse%20Broadnening%20Effect.gif) **Figure 2:  Pulse Broadening Effect3** Over longer distances, this small "dispersion" eventually adds up to a degree that the receiving end cannot properly distinguish between two consecutive signals as the pulses start to overlap: ![Overlapped Signals.jpg](https://www.m2optics.com/hs-fs/hubfs/images/Overlapped%20Signals.jpg?width=640&name=Overlapped%20Signals.jpg) **Figure 3:  Overlapped Signals4** If not managed, this can cause serious trouble in network communication systems, especially in fast bit rate applications. A 40G system is more susceptible to chromatic dispersion than 10G system because the signal pulses are more densely packed at the source. While a 10G system can go up to one hundred kilometers without trouble, a 40G system can go no further than a few kilometers without the requirement for dispersion compensating solutions. (Author's comment: It should be noted that specifications for optical fibers often state a *group refractive index* value, which is based on group velocity, not phase velocity.  As a result, the refractive index value increases as the wavelength increases. [An example of this](https://www.m2optics.com/optical-fibers) can be seen with Corning® SMF-28® Ultra single mode optical fiber, where the RFI @ 1310nm is 1.4676 and @ 1550nm is 1.4682) **How a Dispersion Compensating Module Reduces Chromatic Dispersion ** A dispersion compensating module (or DCM) is used to compensate the cumulative dispersion in a single mode fiber and a dispersion coefficient is used to characterize the dispersion value. The value for regular SMF is around +16~17 ps/(nm*km) at 1550nm. To properly manage this, the DCM is built using a special type of dispersion compensating fiber inside the module that has a negative value of dispersion coefficient, ranging from -30 to -300 ps/(nm*km). As an example, the cumulative dispersion for a 10km length of fiber will be +160~170 ps/nm, so to compensate for that amount of dispersion, a DCM will be added to the link with a specific and calculated fiber length aimed at reducing the total dispersion close to 0 ps/(nm*km). **Want to Learn More?** **[![Contact M2 Optics For Your FREE Fiber Consultation!](https://no-cache.hubspot.com/cta/default/39436/bc77bf9a-2691-4ce1-916b-a26577c4f50d.png)](https://cta-redirect.hubspot.com/cta/redirect/39436/bc77bf9a-2691-4ce1-916b-a26577c4f50d)** Since 2001, M2 Optics has been manufacturing DCMs to support network operators requiring compensation for ITU G.652 single mode fibers. Our experienced team of engineers is available to answer any questions you may have on this topic, or help you to [design a customized solution](https://www.m2optics.com/contact-us) for your specific requirements. * **Article References:* 1. [https://www.rp-photonics.com/fibers.html ](https://www.rp-photonics.com/fibers.html)2. [http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/dispersion.html](http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/dispersion.html) 3. [http://www.thefoa.org/tech/ref/testing/test/CD_PMD.html](http://www.thefoa.org/tech/ref/testing/test/CD_PMD.html) 4. [https://www.newport.com/t/fiber-optic-basics](https://www.newport.com/t/fiber-optic-basics)     Topics: [optical fiber](https://www.m2optics.com/blog/topic/optical-fiber), [dispersion compensating fiber](https://www.m2optics.com/blog/topic/dispersion-compensating-fiber) --- ![M2 Optics, Inc.](https://www.m2optics.com/hubfs/M2%20Optics%2c%20Inc.-%20Transparent.png "M2 Optics, Inc.") ### Subscribe to Email Updates ### Recent Posts ### Posts by Topic - [optical fiber (57)](https://www.m2optics.com/blog/topic/optical-fiber) - [network simulation (28)](https://www.m2optics.com/blog/topic/network-simulation) - [fiber optic testing (19)](https://www.m2optics.com/blog/topic/fiber-optic-testing) - [latency (19)](https://www.m2optics.com/blog/topic/latency) - [fiber monitoring (14)](https://www.m2optics.com/blog/topic/fiber-monitoring) - [optical time delays (14)](https://www.m2optics.com/blog/topic/optical-time-delays) - [otdr (11)](https://www.m2optics.com/blog/topic/otdr) - [fiber optic training (9)](https://www.m2optics.com/blog/topic/fiber-optic-training) - [multimode fiber (8)](https://www.m2optics.com/blog/topic/multimode-fiber) - [PON (7)](https://www.m2optics.com/blog/topic/pon) - [fiber optics (7)](https://www.m2optics.com/blog/topic/fiber-optics) - [fiber optic cable (5)](https://www.m2optics.com/blog/topic/fiber-optic-cable) - [fiber optic networks (5)](https://www.m2optics.com/blog/topic/fiber-optic-networks) - [optical taps (5)](https://www.m2optics.com/blog/topic/optical-taps) - [single mode fiber (5)](https://www.m2optics.com/blog/topic/single-mode-fiber) - [RFoF (4)](https://www.m2optics.com/blog/topic/rfof) - [WDM (4)](https://www.m2optics.com/blog/topic/wdm) - [dispersion compensating fiber (4)](https://www.m2optics.com/blog/topic/dispersion-compensating-fiber) - [fiber lab (4)](https://www.m2optics.com/blog/topic/fiber-lab) - [omi (4)](https://www.m2optics.com/blog/topic/omi) - [Optical fiber market (3)](https://www.m2optics.com/blog/topic/optical-fiber-market) - [optical switching (3)](https://www.m2optics.com/blog/topic/optical-switching) - [3D design (2)](https://www.m2optics.com/blog/topic/3d-design) - [fiber characterization (2)](https://www.m2optics.com/blog/topic/fiber-characterization) - [hollow-core optical fiber (2)](https://www.m2optics.com/blog/topic/hollow-core-optical-fiber) - [multicore optical fiber (2)](https://www.m2optics.com/blog/topic/multicore-optical-fiber) - [1.6Tb/s optical transceivers (1)](https://www.m2optics.com/blog/topic/1-6tb-s-optical-transceivers) - [2024 Paris Olympics (1)](https://www.m2optics.com/blog/topic/2024-paris-olympics) - [3D Printing (1)](https://www.m2optics.com/blog/topic/3d-printing) - [3D design and printing servives (1)](https://www.m2optics.com/blog/topic/3d-design-and-printing-servives) - [3D printing and design for Telecom (1)](https://www.m2optics.com/blog/topic/3d-printing-and-design-for-telecom) - [3d printing and design services for Fiber Optics (1)](https://www.m2optics.com/blog/topic/3d-printing-and-design-services-for-fiber-optics) - [3d rapid prototyping (1)](https://www.m2optics.com/blog/topic/3d-rapid-prototyping) - [5g (1)](https://www.m2optics.com/blog/topic/5g) - [AI (1)](https://www.m2optics.com/blog/topic/ai) - [IOR (1)](https://www.m2optics.com/blog/topic/ior) - [Lightium (1)](https://www.m2optics.com/blog/topic/lightium) - [OM5 (1)](https://www.m2optics.com/blog/topic/om5) - [OM5 wideband multimode optical fiber (1)](https://www.m2optics.com/blog/topic/om5-wideband-multimode-optical-fiber) - [RF-over-Fiber (1)](https://www.m2optics.com/blog/topic/rf-over-fiber) - [Silicon Photonics (1)](https://www.m2optics.com/blog/topic/silicon-photonics) - [TFLN (1)](https://www.m2optics.com/blog/topic/tfln) - [bare optical fiber (1)](https://www.m2optics.com/blog/topic/bare-optical-fiber) - [best practices (1)](https://www.m2optics.com/blog/topic/best-practices) - [blockchain (1)](https://www.m2optics.com/blog/topic/blockchain) - [broadband service (1)](https://www.m2optics.com/blog/topic/broadband-service) - [calculate latency (1)](https://www.m2optics.com/blog/topic/calculate-latency) - [chromatic dispersion (1)](https://www.m2optics.com/blog/topic/chromatic-dispersion) - [cybersecurity (1)](https://www.m2optics.com/blog/topic/cybersecurity) - [data centers (1)](https://www.m2optics.com/blog/topic/data-centers) - [dc fiber (1)](https://www.m2optics.com/blog/topic/dc-fiber) - [dcf (1)](https://www.m2optics.com/blog/topic/dcf) - [drone fiber spool canisters (1)](https://www.m2optics.com/blog/topic/drone-fiber-spool-canisters) - [egaming (1)](https://www.m2optics.com/blog/topic/egaming) - [electric utilities (1)](https://www.m2optics.com/blog/topic/electric-utilities) - [fiber network simulators (1)](https://www.m2optics.com/blog/topic/fiber-network-simulators) - [fiber optic drone (1)](https://www.m2optics.com/blog/topic/fiber-optic-drone) - [fiber tether (1)](https://www.m2optics.com/blog/topic/fiber-tether) - [fusion splice (1)](https://www.m2optics.com/blog/topic/fusion-splice) - [gas and electric (1)](https://www.m2optics.com/blog/topic/gas-and-electric) - [high-index optical fiber (1)](https://www.m2optics.com/blog/topic/high-index-optical-fiber) - [index of refraction (1)](https://www.m2optics.com/blog/topic/index-of-refraction) - [innovation (1)](https://www.m2optics.com/blog/topic/innovation) - [mechanical splice (1)](https://www.m2optics.com/blog/topic/mechanical-splice) - [online gaming (1)](https://www.m2optics.com/blog/topic/online-gaming) - [optical fiber attenuation (1)](https://www.m2optics.com/blog/topic/optical-fiber-attenuation) - [optical fiber reference guide (1)](https://www.m2optics.com/blog/topic/optical-fiber-reference-guide) - [optical fiber tension (1)](https://www.m2optics.com/blog/topic/optical-fiber-tension) - [otdr testing service (1)](https://www.m2optics.com/blog/topic/otdr-testing-service) - [otdr trace (1)](https://www.m2optics.com/blog/topic/otdr-trace) - [otdr training (1)](https://www.m2optics.com/blog/topic/otdr-training) - [pm fiber (1)](https://www.m2optics.com/blog/topic/pm-fiber) - [polarization-maintaining optical fiber (1)](https://www.m2optics.com/blog/topic/polarization-maintaining-optical-fiber) - [quantum computing (1)](https://www.m2optics.com/blog/topic/quantum-computing) - [refractive index (1)](https://www.m2optics.com/blog/topic/refractive-index) - [space division multiplexing (1)](https://www.m2optics.com/blog/topic/space-division-multiplexing) - [submarine fiber cable (1)](https://www.m2optics.com/blog/topic/submarine-fiber-cable) - [thin film lithium niobate (1)](https://www.m2optics.com/blog/topic/thin-film-lithium-niobate) - [transportation network (1)](https://www.m2optics.com/blog/topic/transportation-network) - [types of otdr events (1)](https://www.m2optics.com/blog/topic/types-of-otdr-events) - [universities and research (1)](https://www.m2optics.com/blog/topic/universities-and-research) - [university campus (1)](https://www.m2optics.com/blog/topic/university-campus) [see all](https://www.m2optics.com/blog/how-does-a-dispersion-compensating-fiber-reduce-chromatic-dispersion#) ### ![pin-icon](https://www.m2optics.com/hubfs/M2_Optics_2021/Home/search-pin.png) **Headquarters** 5621 Departure Dr, Ste 117 Raleigh, NC 27616, USA ### ![phone-icon](https://www.m2optics.com/hubfs/M2_Optics_2021/Home/call.png) **Call Us** Phone: [1-919-342-5619](tel:1-919-342-5619) Toll Free: [866-269-2902](tel:866-269-2902) ### ![email-icon](https://www.m2optics.com/hubfs/M2_Optics_2021/Home/email.png) **Email Us** [sales@m2optics.com](mailto:sales@m2optics.com) [![M2 Optics](https://www.m2optics.com/hs-fs/hubfs/M2_Optics_2021/footer-logo.png?width=166&height=58&name=footer-logo.png "M2 Optics")](https://www.m2optics.com/) Offering customized solutions for fiber network simulation, optical time delay, and network testing applications that allow each user to specify exactly what they need. [**](https://www.facebook.com/m2optics/) [**](https://twitter.com/M2Optics) [**](https://www.linkedin.com/company/2288956) ### Subscribe Sign up to get the latest news, current blog posts, and most up-to-date information on fiber optic technology. Copyright © 2021 M2Optics, Inc. All rights reserved. | [Privacy Policy](https://www.m2optics.com/privacy-policy)