Fiber Optic Calculator Help

Field Description.

Cable Length: Total length of optical cable. Real number field, Units:Meters.
Splices: Total number of splices in design. Integer field.
Connectors: Total number of connectors in design. Integer field.

Light Source

Laser: A device which produces a single frequency light. By turning on and off the laser light signal quickly, you can transmit the ones and zeroes of a digital communications channel.

Light Emitting Diode (LED): A semiconductor diode which emits light when a current is passed through it. Used as sources for optical data link applications.

Splice Type

Fusion Splice: A fusion splice is a fiber optic splice made by perfectly aligning the fiber to be spliced, and then applying enough heat to fuse the glass ends together. Typical loss for a fusion splice is less than 0.05 db. The calculator uses 0.01 db.

Mechanical Splice: A mechanical splice is a fiber optic splice made by aligning the fibers to be spliced, and then mechanically binding them together. An index matching gel is placed between the ends of the fibers to assure no air gap is present. Typical loss is less than 1.0 db. The calculator uses a loss of .5 db.

Fiber Cable Type

Single-mode Fiber: Single-mode fiber has one path for the light to travel. The reason is the size of the core is about 8.3 micro.

Multi-mode Fiber: Another name for mode is "path". Multi-mode cable has multiple paths for the light to travel.

General Information

Spectral Width (full width, half maximum spectral power FWHM): is a measurement of the width of the width of the spectrum of light being transmitted by a light source. This is measured in nanometer.

Modal Dispersion: is the widening of the output pulse as a result of different modes requiring different lengths of time to propagate down the fiber. This affects only multi-mode cable.

Chromatic Dispersion: The output effect of chromatic dispersion is similar to modal dispersion but the cause is different. The light source emits light at multiple frequencies, and different frequencies of light propagate at different speeds. Both multi-mode and single-mode optics suffer from this.

Calculation Information.

The following are equations and constants used by the calculator:

Modal Dispersion Cable Bandwidth = BM = (1000*Mhz*Km)/Cable length

Total Chromatic Dispersion = Chromatic Dispersion * FWHM * Cable length.

Where chromatic dispersion used is 6ps/nm*km.

Bandwidth = BD = 0.44/Total Chromatic Dispersion.

For Multi-mode:

Total Optical Bandwidth = sqrt(1/(1/(BM*BM))+(1/(BD*BD)))

For Single mode:

Total Optical Bandwidth = 0.44/Total Chromatic Dispersion

Total Loss = Cable length * cable loss + Number of connectors * connector loss + number of splices * splice loss.

Where.

Cable loss is:

Multi-mode = 0.7 db

Single mode = 0.4 db Splice loss is: Mechanical = 0.5 db Fusion = 0.01 db Connector loss = 0.5db