RP Photonics logo
RP Photonics
Encyclopedia
Consulting Software Encyclopedia Buyer's Guide

Short address: rpp-con.com

Dr. Paschotta, the founder of RP Photonics, supports your R & D with his deep expertise. Save time and money with efficient support!

Short address: rpp-soft.com

Powerful simulation software for fiber lasers and amplifiers, resonator design, pulse propagation and multilayer coating design.

Short address: rpp-enc.com

The famous Encyclopedia of Laser Physics and Technology provides a wealth of high-quality scientific and technical information.

Short address: rpp-bg.com

In the RP Photonics Buyer's Guide, you easily find suppliers for photo­nics products. As a supp­lier, you can profit from enhanced entries!

Learn on lasers and photonics every day!
VL logo part of the
Virtual
Library

Decibel

<<<  |  >>>  |  Feedback

Buyer's Guide

Use the RP Photonics Buyer's Guide to find suppliers for photonics products! You will hardly find a more convenient resource.

Definition: a logarithmic measure for power ratios, applied e.g. to optical powers or to noise powers

German: Dezibel

The decibel (dB) is often used for quantifying the gain of an amplifier or the loss of some optical element, such as an optical fiber or an optical attenuator. The number of decibels is 10 times the logarithm (to base 10) of the power amplification factor or loss factor, or alternatively 20 times the logarithm of the amplitude ratio of the electric field strengths.

Such a logarithmic quantity is useful because e.g. the decibel gain values of several amplifiers in a sequence can simply be added to obtain the total gain of the amplifier chain.

decibel scale

Figure 1: Scale for converting decibels to power amplification factors and vice versa.

Decibels in the Context of Optical Signals

The decibel is also often used in the context of transmitted signals (e.g., for optical filters) and of noise e.g. of lasers or amplifiers. Great care is recommended in the context of optical signals, where one is dealing with two different kinds of power:

For example, if the peak-to-peak modulation of an optical power is increased by a factor of 10 (e.g. by amplification in a 10-dB fiber amplifier), this increases the signal power by 20 dB, not 10 dB.

Frequently Used Specifications

Some frequently used related specifications are:

See also: gain, amplifiers

Category: metrology

How do you rate this article?

Your general impression: don't know poor satisfactory good excellent
Technical quality: don't know poor satisfactory good excellent
Usefulness: don't know poor satisfactory good excellent
Readability: don't know poor satisfactory good excellent
Comments:

Found any errors? Suggestions for improvements? Do you know a better web page on this topic?

Spam protection: (enter the value of 5 + 8 in this field!)

If you want a response, you may leave your e-mail address in the comments field, or directly send an e-mail.

If you like our website, you may also want to get our newsletters!

arrow

Have you seen the
RP Photonics Buyer's Guide?

It lists many hundreds of suppliers for photonics products, and is just one mouse click away from the extremely popular Encyclopedia of Laser Physics and Technology:

Our Buyer's Guide is what you need:

And surely you will remember where to find this useful resource again!

Suppliers: get your free entries, and enhanced visibility with paid entries.

Stay Up to Date with Newsletters

Obtain the Photonics Spotlight and the RP Photonics Software News as a newsletter! We spread interesting information, not just advertisements.

Laser Design Services

Fast and efficient laser development is possible with the competent design services of RP Photonics, based on extensive experience, deep scientific knowledge and advanced software.

Thin-film Optics Software

Analyze and optimize dichroic and dispersive mirrors, AR coatings, filters, thin-film polarizers, rugate filters, VECSELs etc. with RP Coating!

coating design

New Fiber Optics Software!

RP Fiber Calculator software

RP Fiber Calculator – a convenient tool for calculations on optical fibers -- offered for free within the 10-year anniversary of RP Photonics, and also as a PRO version with even more powerful features!

Tailored Training Courses

Within one or two days, a tailored training course at your location can boost the competence of your team. An investment which can pay back very rapdily!