ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Fiber Optics/Optical Fiber Losses

Updated on August 19, 2015


Optical fiber communication system works same as any other telecommunication system difference being instead of electrical signals travelling through metal cables, light carries information in glass fibers. Fig 2.1.a describes a simple telecommunication system consisting of information source, transmitter, channel and a receiver. Fig 2.1.b describes an optical fiber communication system.
Main components of an Optical Fiber Communication System are

  1. Information Source: Usually a person or computer or any entity which want to send information to the receiver.
  2. Transmitter : It consists of three stages. Firstly the information from the information source is converted into corresponding electrical signals. These electrical signals then drive an optical source(LED/LASER) modulate the light signal.
  3. Optical Fiber (Channel): Optical fibers are mainly glass or plastic fibers used for propagation of light over large distances. The propagation of light through the fiber is based on the principle of total internal reflection.
  4. Receiver: Receiver as transmitter also has three stages. The optical detector (LDR/Photodiode) detects the incoming optical signal and drives the electrical receive to convert optical signal into electrical signal and deliver it to the recipient using suitable transducer.
  5. Connectors: They are used for connection between two fibers or transmitter to fiber or fiber to receiver connections.


Also known as transmission loss. It can be defined as the loss of optical power when light travels long distances inside a transmission medium is known as attenuation. It is defined as the ratio of the optical input power (Pi) and optical output power (Po) .

Attenuation = (10/L)log10(Pi/Po)

Unit of attenuation is db/Km

Absorption Losses

One of the major forms of signal loss in optical fiber. When light travels in the glass/fiber medium impurities in the channel such as metal particles or moisture in the fiber can block some of the light, absorb it and dissipate light in form of heat resulting in loss. So absorption loss can be defined as the portion of signal loss due to its conversion into other forms of energy such as heat. It’s of two types namely: -

  1. Intrinsic Absorption: It is cause by the basic fiber-material properties. If we consider the fiber to free all the impurities and imperfections then all losses would be intrinsic. These can be overcome only by changing the fiber material.In silica glass, the wavelengths of operation range from 700 nanometers (nm) to 1600 nm. So for silica in the wavelength regions of interest for optical communication infrared absorption tails makes negligible contributions..

Intrinsic Absorption

Impurity Ion
Loss due to 1ppm of impurity (dB/km)
Absorption Peak Wavelength (um)
Attenuation due to impurities

2. Extrinsic Absorption : It is caused by the presence of impurities in the fiber like metal ions such as Fe2+, Cu2+, Cr3+ or presence of hydroxyl ions (OH-) i.e. silicon-hydroxyl (Si-OH) bond inside the fiber. For lower losses (<1dB/km) the metal impurities should be below part per billion.Using dry fibers the OH ion concentration is reduced and we can see the peak at 1.39um disappears.

Scattering Losses

Light propagation inside the fiber is based on total internal reflection. Any irregularity even molecular-level irregularities in the surface of the fiber can cause the light to reflect light in random directions and results in scattering losses. It can be divided into two categories namely

  1. Linear scattering
  2. Non- Linear scattering.

  1. Linear scattering

1.1 Rayleigh Scattering: It is one of the main causes of fiber optic losses. In molten state the silica molecules move randomly and freeze at one place in solid state. This causes fluctuation in the density and consequently fluctuations in refractive index occur throughout the fiber. Scattering of light due to this is known as Rayleigh scattering and it result to 96% of the optical fiber losses.

1.2 Mie Scattering: Scattering of light can also occur if the inhomogeneities in the fiber are comparable to the guided wavelength. It is due to the imperfections in the cylindrical structure of the waveguide such as irregularities in the core–cladding interface, core–cladding refractive index differences along the fiber length, diameter fluctuations, strains and bubbles.

Rayleigh Scattering
Rayleigh Scattering

Non-linear scattering losses

These type of losses occur due to the inelastic scattering of a photon to a lower energy photon i.e. the energy of the light signal is transferred to another wave of higher wavelength but lower energy. The energy difference results into a photon.
Non-Linear scattering is of two types

  1. Stimulated Raman scattering (SRS)
  2. Stimulated Brillouin scattering (SBS).

1.1 Stimulated Brillouin Scattering (SBS): Comes in effect at higher frequencies. When modulation of light happens due to thermal vibration inside the fiber it results in SBS. The scattering produces a acoustic photon which produces an optical frequency shift of around 10 GHz known as Stokes shift. Occurs only in backward direction.

1.2 Stimulated Raman scattering (SRS): It is similar to Brillouin scattering difference being that instead of an acoustic photon an optical photo is generated. Also it can occur in both forward and backward direction and can have an optical threshold of upto three times the magnitude compared to Brillouin scattering. It has a frequency shift of around 13 THz.

Bending Losses:

As the name suggests these losses occurs due to bending of fiber as it disrupts the path of light signal. It’s of two types namely

  1. Macro bends
  2. Micro bend losses.

1.1 Macro bends: The folding of optical fibers into tight bends is known as macrobends. This creates an angle too sharp that some of the light is not reflected back into the fiber and escapes the cladding resulting in loss of signal. The optical loss increases as the radius of the fiber is decreased. Different fibers have different specificatiosns on the amount of permissible bends without significant loss of signal. For G.657.B.3 fiber standard (International Telecommunication Union) the radius has been standardized as low as 5mm.

1.2 Micro bends: Small bends which are caused by pinching or squeezing of the fiber which leads to deformations in the fiber structure. This results in displacement of light and hence causes optical loss. [Halit Eren. "Optical Loss."]

Macro Bend

Micro Bend

Dispersion Losses:

Dispersion is described as the broadening of light pulses. It is the result of physical properties of the system. It’s of three types namely

  1. Model dispersion
  2. Material dispersion
  3. Wave-guide dispersion

1.1 Modal Dispersion: It occurs in multi-mode fibers only as in single mode fibers there is only one signal pulse. In multi-mode fibers as it has a larger core size it can guide several modes simultaneously. Each mode enters the fiber at different angles and travel different distance towards the receiver. During time the light waves spreads and this may lead to overlapping of the signals hence causing distortions in the signals.

1.2 Material dispersion: It occurs due to the fact that the spreading of light is dependent on the interaction of light with the refractive index of the fiber material i.e. Every wavelength travel with different speed inside the fiber and spreading of light depend on its wavelength.

1.3 Wave-guide dispersion: This type of dispersion mainly occurs in single mode fibers. This happened due to the reason that some part of light travel in cladding and most part of light travel inside the core. Due to the difference in the refractive index of both core and cladding. The light in each travel at different velocities hence causing spreading of light at receiver.

Modal Dispersion

Material dispersion:

Wave-guide dispersion

Connector losses

These type of losses occur at the interconnection of two fibers. It can happen if the connection between the fiber is misaligned or has air-gap or have unequal diameter or have tilted axis. The types of connector losses are depicted in the fig.

Connector losses

Cast your vote for OFC Losses


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)