The optical power budget in a
fiber-optic communication link is the allocation of available optical
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
(launched into a given fiber by a given source) among various loss-producing mechanisms such as launch
coupling loss
Coupling loss, also known as connection loss, is the loss that occurs when energy is transferred from one circuit, circuit element, or medium to another. Coupling loss is usually expressed in the same units—such as watts or decibels—as in t ...
, fiber
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variabl ...
, splice losses, and
connector losses, in order to ensure that adequate
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
strength (optical power) is available at the receiver. In optical power budget attenuation is specified in
decibel (dB) and optical power in
dBm
DBM or dbm may refer to:
Science and technology
* dBm, a unit for power measurement
* DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB
* Database Manager (DBM), a component of 1987's ''Extended Edi ...
.
The amount of optical power launched into a given fiber by a given transmitter depends on the nature of its active optical source (
LED or
laser diode
The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...
) and the type of
fiber
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...
, including such parameters as
core diameter and
numerical aperture. Manufacturers sometimes specify an optical power budget only for a fiber that is optimum for their equipment—or specify only that their equipment will operate over a given distance, without mentioning the fiber characteristics. The user must first ascertain, from the manufacturer or by testing, the
transmission losses for the type of fiber to be used, and the required signal strength for a given level of performance.
In addition to
transmission loss
Transmission loss (TL) in general describes the accumulated decrease in intensity of a waveform energy as a wave propagates outwards from a source, or as it propagates through a certain area or through a certain type of structure.
It is a termino ...
, including those of any splices and connectors, allowance should be made for at least several dB of
optical power margin losses, to compensate for
component
Circuit Component may refer to:
•Are devices that perform functions when they are connected in a circuit.
In engineering, science, and technology Generic systems
* System components, an entity with discrete structure, such as an assem ...
aging and to allow for future splices in the event of a severed
cable
Cable may refer to:
Mechanical
* Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof
* Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
.
:''L''
T = ''αL'' + ''L''
c + ''L''
s
Definitions:
*''L''
T - Total loss
*''α'' - Fiber attenuation
*''L'' - Length of fiber
*''L''
c - Connector loss
*''L''
s - Splice loss
Passive optical network
A passive optical network (PON) is a fiber-optic telecommunications technology for delivering broadband network access to end-customers. Its architecture implements a point-to-multipoint topology in which a single optical fiber serves multiple e ...
s use optical splitters to divide the downstream signal into up to 32 streams, most often a power of two. Each division in two halves the transmitted power and therefore causes a minimum attenuation of 3 dB (
≈ 10
−0.3).
References
{{FS1037C
External links
Fiberoptic power budget calculator
Fiber-optic communications