A NEW APPROACH TO REMOTE FIBER TESTING IN OPTICAL NETWORKS. University of Zagreb, Faculty of Electrical Engineering and Computing

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1 A NEW APPROACH TO REMOTE FIBER TESTING IN OPTICAL NETWORKS Krešo Žmak University of Zagreb, Faculty of Electrical Engineering and Computing

2 Outline Introduction New approach to RFTS System architecture Error correction method Measurement results Summary

3 Introduction Optical communication systems (OCS) form the basis of all telecommunication networks The development of OCS was followed by the development of Remote Fiber Testing Systems (RFTS) The price of the current RFTS exceeds the price of local and access networks Error-detection and error-correction raise to few days, even weeks New RFTS a low-cost and reliable tool for error detection in local and access networks

4 Measurement system The new system represents the fundamental (simplest) form of the future test system Main purpose Error detection in OCS (mechanical( faults or quality losses in optical fibers or connectors) Main idea Modification of the current RFTS in order to lower it s price Current RFTS OTDR as main measurement unit Optical Switch Software control New RFTS OTDR as main measurement unit Optical power splitter Software control

5 Measurement system architecture Measurement unit OTDR Optical power splitter Control unit PC Software Pre-measurement management Post-measurement management Serial interface connection (RS232)

6 1. Measurement setup 2. OTDR launches the pulse 3. Input power is divided Measurement process 4. Output pulses travel through the fiber 5. All scattered and reflected signals form a complex measurement trace 6. OTDR trace saved in the computer memory 7. Measurement analysis

7 Error detection reference measurement Based on comparison of reference and test measurements Reference measurements performed after the installation of the OCS Measurement points defined at characteristic events on the OTDR trace (splices, fiber end, connector reflections)

8 Error detection measurement comparison Error : The difference of the power level between the test and reference measurements,, at the measurement points, exceeds a predefined treshold level Test measurements automaticaly performed in time intervals which vary from 1 min to 1 hour

9 RFTS management software Specially developed for the new system The program was developed using the Microsoft TM Visual Basic TM software package Three modules Main module Comparison module Automatic test module The program partition enables a simple and fast software management

10 Functions : Main module Measurement setup (OTDR setup) Wavelenght (nm) Output pulse width (ns) Averaging time (s) Spatial resolution (number of samples) 1310, ,20,50,100 1 to ,50000 Reference measurement control Measurement points definition User-friendly interface easy and efficient measurement points definition

11 Main module user interface

12 Comparison module Functions : Test measurement control Test measurement result analysis Error detection Automatic error detection based on comparison of test and reference measurement results Graphical User interface : reference waveform window test waveform window difference waveform window both waveform window

13 Comparison module user interface

14 Automatic test module Modified version of the comparison module Fully automatized test measurements and error detection Module parameters : Measurement repetition time interval Error treshold level

15 Measurement results Wavelenght,, pulse width and power ratio dominantly influence the measurement results Measurement parameters values : Power splitter Pulse width (ns) Wavelength (nm) Test fibers (m) 50/50 75/25 90/ / /3000 (5m difference ) Power splitter 90/10 simulates the case where the power is equally divided to 10 fibers As error case we disconnected one fiber

16 Error detection for fibers with similar lenght Test fiber (m) Power splitter Wavelength (nm) Pulse width (ns) Error detection / No 1550 No / /25 No 1550 No /10 No 1550 No

17 Error detection for fibers with different lenght Test fiber (m) Power splitter Wavelength (nm) Pulse width (ns) Error detection / / / /

18 Summary The new RFTS a modification of the current RFTS Parralel fiber testing using the power splitter Tests confirmed the system efficiency Future : Active optical network Error location method

There are lots of problems or challenges with fiber, Attenuation, Reflections, Dispersion and so on. So here we will look at these problems.

There are lots of problems or challenges with fiber, Attenuation, Reflections, Dispersion and so on. So here we will look at these problems. The Hard theory The Hard Theory An introduction to fiber, should also include a section with some of the difficult theory. So if everything else in the book was very easily understood, then this section