Coupling Losses/Connector losses:

• In fiber cables, coupling losses can occur at any of the following three types of optical junctions- light source to fiber connection, fiber to fiber connections and fiber to photo detector connections. Junction losses are most often caused by one of the following alignment problems

Lateral Misalignment:

• The lateral or axial displacement between two pieces of adjoining fiber cables is as shown in the figure. The amount of loss can be from a couple of tenth of a decibel to several decibels. This loss is generally negligible if the fiber axes are aligned to within 5% of the smaller fiber diameter.

Gap Misalignment:

• This is sometimes called as end separation as shown in figure. When splices are made in OF’s, the fibers should actually touch. The farther apart the fibers are, the greater the loss of light. If two fibers are joined with the connector, the ends should not touch. This is because two ends rubbing against each other in the connector could cause damage to either or both fibers.

Angular Misalignment:

• This is shown in figure and is sometimes called angular displacement. If the angular displacement is less than 2°, the loss will be less than 0.5dB.

Imperfect Surface finish:

• This is shown in figure. The ends of the two adjoining fibers should be highly polished and should fit together squarely. If the fiber ends are less than 3° off from the perpendicular, the losses will be less than 0.5dB.