Project Description

February 9th 2014 –

Optical receiver for AMA 310

The optical receiver input to measure signals in fiber-optic lines, is ready to be shipped soon. As always with KWS: in addition to the installation into new devices all existing units AMA 310 can be retrofitted.

RF signals are increasingly being transmitted via fibre optic cables – optical transmission in broadband networks is gaining importance. While optical transmission in most existing networks still occurs exclusively at network level 2, the trend is moving towards fibre optic distribution up to the subscriber terminals. Also in the field of SAT-IF distribution, solutions are available for optical transmission.

Optical fibres: the optical fibre is the medium through which the light signal is transmitted. There are 2 different fibre types. With multi-mode fibres, the light can move through the optical fibres on multiple »paths« (modes). This results in modal dispersion (distortion), which limits the bandwidth and the transmission distance. With single-mode fibres, on the other hand, the light can only move through the fibres on a single path, preventing modal dispersion and resulting in higher bandwidths.

At the moment, almost all the fibres used are single-mode. They have a core diameter of 9 µm and a sheath diameter of 125 µm. A single-mode optical fibre has an attenuation of approx. 0.3 dB/km. The measuring instrument is equipped with an optical receiver that converts the light signal back into an RF signal. After the optical receiver, the RF signal behaves as if it had been supplied via the coax input of the measuring receiver.

This means that all the measurements available through the RF input can also be taken via the optical input. There is one restriction: For DOCSIS, only the downstream can be measured because the device does not have an optical transmitter for the upstream.

Specifications for the option:

Connector: SC/APC (with protective cap)
Wavelength (Lambda): 1,260–1,620 nm (no optical filter)
Max. optical input power: +8 dBm (continuous power)
Return loss: > 40 dB
Equivalent Input Noise (ON): < 8 pA/√Hz
RF frequency range: 5–2,150 MHz
Input power nominal: -7…+3 dBm

Measuring parameters
Optical power: -35 dBm to +9 dBm
Wavelength (calibrated): 1,310 nm / 1,490 nm /1,550 nm
Resolution: 0.1 dB
Measuring accuracy: ± 0.25 dB

Optical modulation index (OMI): individual OMI and total OMI
Resolution: 0.1 %
Measuring accuracy: ± 10% (of displayed value)

Block diagrams of the measurement methods.

DVB-S/-S2 measurement in AMA 310 with optical input

KWS-Electronic optic AMA 310: Block diagram DVB-S/S2

DVB-C and DOCSIS-DS measurement in AMA 310 with optical input

KWS-Electronic optik AMA 310: Block diagram CATV

DVB-T/-T2/-DAB measurement in AMA 310 with optical input

KWS-Electronic optik AMA 310: Block diagram DVB-T/T2

FM/TV signal measurement in AMA 310 with optical input

KWS-Electronic optik AMA 310: Block diagrams FM,BK,TV