IEC 61300-3-26:2002 pdf download

IEC 61300-3-26:2002 pdf download.Fibre optic interconnecting devicesand passive components – Basic test and measurement procedures -Part 3-26: Examinations and measurements- Measurement of the angular misalignmentbetween fibre and ferrule axes.
This part of IEC 61300 describes the procedure to determine the angular misalignment between the fibre and the ferrule axes in a cylindrical ferrule for singiemode fibre optical connectors with fibre installed.
General description
This procedure describes the measurement of the angular misalignment between the fibre and the ferrule axes in a cylindrical ferrule for fibre optic connectors with fibre installed. Angular misalignment is defined as the angle J between the axis of the ferrule and the axis of the installed fibre (see Figure 1).
This procedure measures angular misalignment by measuring the deviation in the far field pattern coming from the core as the ferrule is rotated around its axis.
Figure 1 — Definition of the fibre misalignment angle
In a optical connector typical values of angular misalignment are in the range of tenths of a degree. At 5 mm from the ferrule surface, the diameter of the light spot (white light) is about 1 mm. On rotating the connector the displacement of the spot is of the order of 11100 of the spot diameter (45 pm for an angular misalignment of 0,5k at 5 mm from the fibre surface).
To detect such a displacement a high precision, automatically controlled set-up Is necessary.
The deviation of the spot coming from the fibre is also affected by the tilt of the fibre surface with respect to the ferrule axis. This deflection is described by SneIls law. It is possible to calculate the contribution due to the tilt of the fibre surface from the curvature radius and the apex offset eccentricity. Some notes and explanation about the equations used in this document to correct this effect are given in Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
Iso 2538, Geometrical Product Specifications (GPS) — Series of angles and slopes on prisms
3 Apparatus
The apparatus, shown in Figure 2, consists of the following elements:
3.1 Ferrule holder
The ferrule is placed and rotated in a precise V-groove holder or in a centring mechanism. According to ISO 2538 the preferred angle for the V-groove is 108°.
3.2 Light source
A white light source is used.
3.3 Screen
The spot from the fibre is projected on a screen. The screen could be the CCD chip of a video
camera. The screen shall be perpendicular to the axis of the V.groove or centring mechanism.
3.4 Data processing equipment
A computer, with suitable software, processes the images from the video camera and analyses the acquired data.
4 Procedure
Before the measurement of the angular misalignment, the radius of curvature, dome apex offset value and its position relevant to the fibre core shall be measured on the ferrule under test. The direction of the fibre core with respect to the dome offset shall be marked on the ferrule (see Figure 3).
The ferrule is placed in the holder with the marker of the dome offset — fibre core direction in a known position. In this way it will be possible to evaluate the light spot position, given by the angle fi, with respect to this marker.
Figure 3 — Position of the marker to indicate the dome vertex — fibre core direction
The ferrule is rotated in steps of 9Q0 or less, until a complete rotation is made. At each position the outline of the light spot is acquired and the centre position is estimated by means of a fitting procedure.
When the centre coordinates of each ferrule position are acquired, the circle that best fits these points shall be found.