scope:

General

This guideline specifies requirements to be met by optical metrology, defines instrumentation standards, and describes methods for practical verification of the above-mentioned requirements. 

Measuring equipment and test parameters

The essential characteristics of a test system are listed below: 

Measurement transmitter 

Peak wavelength of test light λ₀

Full width at half maximum λ_FWHM 

Radiation pattern (corresponds to A_N)

Transmitted power and temperature stability 

Stability of radiation pattern in the direction of expansion 

Launch geometry 

Output geometry 

Measurement receiver 

Optically active surface area 

Linearity over the working range of the system 5.3 Suitability for the range of wavelengths of the system 

Maximum detectable angle of light incidence 

Spectral correction (see Annex A2.10)

Note 1: As a matter of principle, product tests serve to verify compliance of the typical characteristics of the specimen with its specification. In the case of POFs, however, the variety of product characteristics is such that it is convenient to relate tests to the intended application of the product (e.g. α = f (λ, mode distribution), i.e. test of attenuation at the wavelength and mode distribution relevant to the intended application).

Note 2: Two types of tolerances must be distinguished when performing tests, and must be considered separately in the power budget of the application: tolerance of the specimen and tolerance of the test system.

Note 3: The launch and output geometries are chosen depending on the system.

Note 4: In order to obtain the best possible accuracy of measurement, the connector system tolerance shall, if possible, be excluded during series testing (see Section 2.3). This means that the ferrules may be fixed individually. (See Figure 1: Tolerances in relative position of the ferrule with respect to the connector do not arise.)

Standardization of POF metrology using sets of parameters

Below, POF metrology is standardized by using socalled "parameter sets as per VDI/VDE 5570" in order to obtain the required comparability of the measured values.

By reducing the multitude of parameter combinations encountered in practice, this convention allows the manufacturers of test systems, purchasing agents, and users to communicate efficiently.

To this end, each of the characteristics of a test system, listed under Section 1.1, is allocated a value corresponding to the intended application of the POF under test. This ensures practical relevance, and prevents, e.g., that a POF intended to transmit the light of a green LED is tested using the light of a red diode laser.

(The theoretical potential of such testing with impractical light are not discussed in detail here. As a matter of principle, such a procedure is not recommended.)

Note: If further widely used applications arise, requiring new parameter combinations, please propose a new parameter set to:

Verein Deutscher Ingenieure e.V.

Kompetenzfeld Optische Technologien

Graf-Recke-Straße 84

40239 Düsseldorf GERMANY

The user will have to decide in each case whether the testing task at hand can be solved, and, if so, which is the appropriate parameter set to be used. The applications listed below are for guidance only.

Where actual conditions of the testing task result in contradictory facts, deviations shall be documented, all equipment shall be calibrated in accordance with the deviations and shall be labelled, and reference shall be made to the documented deviations wherever the measured values are used.

The manufacturer of a test system shall document the tolerances of these parameters as per Section 1.1, or the influence of these tolerances, in such a manner that errors can be analysed in accordance with Annex A5 or Annex A6 without further research.

Currently specified sets of parameters:

• Parameter set 1 (e.g. for POF networks in motor vehicles)

• Parameter set 2 (e.g. for POF connections in automation and building networks)

Specification of parameter set 1 as per VDI/VDE 5570: Applications in motor vehicles

Measurement transmitter 

Peak wavelength of test light λ₀ : 650 nm ±10 nm (thermally stable) 

Full width at half maximum λFWHM: 25 nm ±5 nm 

Radiation pattern (corresponds to AN): 0,50 ± 0,02 ideally: UMD; actually: uniform mode distribution within the acceptance range of the POF ±20% 

Transmitter power, thermostabilised: ≥ -15 dBm (monitored and controlled)