fiber properties (original) (raw)
Author: the photonics expert (RP)
Category: 
fiber optics and waveguides
- fiber properties
- acceptance angle
- bend losses
- cut-off wavelength
- differential mode delay
- effective mode area
- effective refractive index
- group velocity dispersion
- intermodal dispersion
- modal bandwidth
- mode radius
- polarization beat length
- propagation constant
- propagation losses
- V-number
- waveguide dispersion
- zero dispersion wavelength
- (more topics)
Related: fibers
DOI: 10.61835/c78 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
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Optical fibers have a range of properties, for which we give a brief overview:
| Property | Symbol | Units | Definition |
|---|---|---|---|
| acceptance angle | ($\theta_{\rm a}$) | rad | the maximum incidence angle of a light ray which can be used for injecting light into a fiber core or waveguide |
| bend losses | propagation losses in an optical fiber (or other waveguide) caused by bending | ||
| cladding diameter | ($d_{\rm cl}$) | μm | the diameter of the fiber cladding |
| coating type | the type of fiber coating | ||
| core diameter | ($d_{\rm co}$) | μm | the diameter of the fiber core |
| cut-off wavelength | ($\lambda_\textrm{co}$) | nm | a wavelength above which a guided mode of a waveguide ceases to exist |
| differential mode delay | DMD | ps/km | the range of time delay values for signals in a telecom fiber (related to intermodal dispersion) |
| effective mode area | ($A_\textrm{eff}$) | µm2 | a quantitative measure of the area which a waveguide or fiber mode effectively covers in the transverse dimensions |
| effective refractive index | ($n_\textrm{eff}$) | 1 | a number quantifying the phase delay per unit length in a waveguide, relative to the phase delay in vacuum |
| group velocity dispersion | ($\beta_2$)($D_\lambda$) | s2/mps/(nm·km) | the frequency dependence of the group velocity in a medium, or (quantitatively) the derivative of the inverse group velocity with respect to angular frequency or wavelength |
| intermodal dispersion | the phenomenon that the group velocity of light propagating in a waveguide structure depends on the waveguide mode | ||
| modal bandwidth | ($B \times L$) | MHz km | the maximum optical bandwidth (limited by intermodal dispersion) which can be used in a telecom fiber |
| mode radius | ($w$) | m | a measure of the transverse extent of a laser mode or laser beam |
| polarization beat length | ($L_{\rm B}$) | m | the period of interference effects in a birefringent fiber |
| propagation constant | ($\beta$) | rad/m | a mode- and frequency-dependent quantity describing the propagation of light in a medium or waveguide |
| propagation losses | ($\alpha$) | dB/km | losses of optical energy during propagation of light |
| refractive index profile | the transverse profile of the refractive index, determining the mode properties | ||
| V-number | ($V$) | 1 | a normalized frequency parameter, which determines the number of modes of a step-index fiber |
| waveguide dispersion | chromatic dispersion arising from waveguiding effects | ||
| zero dispersion wavelength | ($\lambda_0$) | nm | a wavelength where the group velocity dispersion of a fiber or a material is zero |
Most of these fiber properties are guided mode properties, i.e., properties of their propagation modes, which are determined by their refractive index profile.
For active fibers, some additional properties are relevant:
| Property | Symbol | Units | Definition |
|---|---|---|---|
| doping concentration | ($N_\textrm{dop}$) | m–3 | the concentration of some dopant, usually of laser-active ions in the fiber core |
| pump cladding diameter | ($d_{\rm pump}$) | m | the diameter of the pump cladding (for double-clad fibers and triple-clad fibers) |
| saturation energy | ($E_{\rm sat}(\lambda)$) | J | a measure of the incident optical pulse energy required for achieving significant saturation |
| saturation power | ($P_{\rm sat}(\lambda)$) | W | a measure of the incident optical power required for achieving significant saturation |
| transition cross-sections | ($\sigma_{\rm abs}(\lambda)$), ($\sigma_{\rm em}(\lambda)$) | m2 | material parameters for quantifying the likelihood or rate of optical transition events |
| upper-state lifetime | ($\tau$) | s | the lifetime of the population in the upper laser level |
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