IEC 61280-2-1 pdf download – Fibre optic communication subsystem test procedures – Part 2-1: Digital systems – Receiver sensitivity and overload measurement

IEC 61280-2-1 pdf download – Fibre optic communication subsystem test procedures – Part 2-1: Digital systems – Receiver sensitivity and overload measurement
As a minimum requirement the data generator shall be capable of providing the followingoutput date formats; other data formats may be used in compliance with the system
requirements.
.a 223-1 pseudo-random data stream;an all 1 data stream;
a 1 + 15 zeros data stream.
The format (pulse shape, amplitude, etc.) of the test signal shall be compliant with thatrequired at the transmit input interface. The receiver portion of the test equipment shall beable to interface with the system output for the measurement of digital errors.
3.2.2Error counter
The error counter of the BER test set shall be able to interface with the output of the EUT. ltshall be capable counting single errors or errored blocks at the data rate of system outputinterface of the EUT. lf the error counter has the facility for computing the BER or EBR valueit must be capable of calculating a value as low as 10-12.
3.3Optical power meter
The optical power meter used shall have a resolution of at least 0,1 dB, shall be data formatand bit rate independent and shall have been calibrated for the wavelength and power rangeof operation for the equipment to be tested.All measurements shall be recorded on the dBscale.
3.4Variable optical attenuator
The optical attenuator shall be capable of attenuation in steps less than or equal to 0,25 dBand should be able to provide a total attenuation that is at least 5 dB greater than the
specified input range of the receiver under test. Care should be taken to avoid back reflectioninto the transmitter.
3.5Optical splitter
The optical splitter (coupler) shall have one input port and two output ports equipped withappropriate connectors.The splitting ratio for the output ports should be 50 %±0,1 dB(unless otherwise specified).
3.6Test cords
Single-mode or multimode fibre reference test cords and fitted with the appropriate
connectors as required by the application shall be used, unless otherwise agreed.The opticalloss of the test cords including connectors shall not exceed 1,0 dB.
3.7Optical transmit interface
The optical transmit interface shall have electrical and optical characteristics similar to thoseof transmitters that are used in the specified fibre optic terminal devices, except that theoutput power shall exceed the maximum specified input power of the receiver by at least2 dB.
4Equipment under test(EUT)
The EUT shall be a fibre optic receiver, optical amplifier or optical regenerator, including allassociated signal conditioning, processing and multiplexing equipment used in the systemunder normal operating conditions.The system input and output terminations shall be thosenormally seen by the user of the system.
5 Test procedure
The test procedure consists of the following steps.
5.1Operating conditions and test environment
Unless otherwise specified, normal operating conditions apply.The ambient or reference pointtemperature and humidity shall be specified.
Switch on the EUT and all test equipment (apply any special operating conditions to the EUTif required) and allow 30 min.(uniess otherwise specified) for the equipment to reach a
steady-state temperature and performance condition.
5.2Connector end-face cleaning
Whenever optical connections are changed, the end faces of the connectors shall be cleaned.Cleaning equipment (including apparatus, materials,and substances) and the methods to beused shall be suitable for the connectors to be cleaned.Connector suppliers’ instructionsshall be consulted where doubt exists as to the suitability of particular equipment andcleaning methods.
5.3Measurement of input sensitivity
Connect the equipment as shown in Figure 2, if terminal equipment is tested, or Figure 3, if anamplifier or regenerator is tested, and set the data generator and error counter to operate witha pseudo random sequence with word length of 2 23-1 (unless otherwise specified).