IEC 61300-3-19:1997 pdf download

IEC 61300-3-19:1997 pdf download.Fibre optic interconnecting devices and passive components – Basic test and measurement procedures
1 General
1 .1 Scope and object
This part of IEC 1 300 describes the test to determine the dependence of return loss of a
singlemode fibre optic component on the state of polarization (SOP) of the light passing
through the component. Return loss is the absolute value of the ratio in decibels of the total
reflected power to the incident power from an optical fibre link or system. Since the SOP of
light in a component is generally indeterminate and in fact often changing as a function of time,
a component that exhibits polarization dependence will have varying return loss in a system.
This procedure can be applied to any singlemode passive component and interconnecting
device, including attenuators, isolators, branching devices, switches, connectors, and splices, if
applicable.
1 .2 Normative reference
The following normative document contains provisions which, through reference in this text,
constitute provisions of this part of IEC 1 300. At the time of publication, the edition indicated
was valid. All normative documents are subject to revision, and parties to agreements based
on this part of IEC 1 300 are encouraged to investigate the possibility of applying the most
recent edition of the normative document indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 875-1 : 1 996, Fibre optic branching devices – Part 1 : Generic specification
2 General description
The measurement is made by comparing the optical power incident on the device under test
DUT with the optical power reflected along the incident path when the optical power with
certain SOP is launched into the DUT. The comparison is made under different SOP. In the
measurement, the DUT is usually a pigtailed fibre optic component. Both the optical power
launched into the input port and reflected from the device along the incident path are monitored
by tapping some of the power respectively through a polarization independent branching
device. The comparison is generally facilitated by the use of automated data acquisition.
Two methods for measuring the polarization dependence are described.
2.1 Method A
Method A will determine the maximum polarization sensitivity over all possible polarization
states. Light is launched into the input port of the DUT such that linear, circular, and elliptical
states of polarization with different axes of orientation can be adjusted while the power from
the output ports is monitored. By adjusting for the maximum and minimum power through the
DUT, the SOPs can result in the highest and lowest return loss of the DUT. Method A is
preferred, particularly for any device in which the SOP of light passing through the device is
changed.
2.2 Method B
Method B will determine the maximum polarization sensitivity over all linearly polarized launch
state of light passing through the device. Method B will generally understate the polarization
sensitivity of return loss of devices which are not dependent on linearly polarized light. In this
method, linearly polarized light is launched into the input port of the DUT. The linear SOP of
the launch is typically rotated through a minimum of 1 80° while the power reflected from the
device under test is measured. If the input port of the DUT contains an integral fibre or cable
pigtail, the pigtail shall be deployed in a straight line without any external stresses, for example
bends, twists, kinks, or tension. This is necessary because the state of polarization carried in
the fibre is altered by external stresses. 1 )
3 Apparatus
The following apparatus and equipment are required to perform this test:
3.1 Optical source
A laser source capable of producing the spectral characteristics defined in the detail
specification (both wavelength and spectral width) shall be used. Unless specified in the detail
specification, the spectral width shall be less than 1 0 nm.
The source power shall be capable of meeting the dynamic range requirements of the
measurement when combined with the detector sensitivity.
The power shall be capable of being modulated or unmodulated as specified in the detail
specification. The power and wavelength stability of the source shall be sufficient to achieve
the desired measurement accuracy over the course of the measurement. Unless otherwise
specified, the power stability shall be within 0,05 dB.
NOTE – Multimode lasers may not provide sufficient polarization stability required for this measurement.