Annual: 2018

EM043 »
Optical Continuous Signal Reflectometer
📁Other: measurements, monitoring
👤Daryna Dyka
 (Just For Fun)
📅May 29, 2018
Semifinalist


👀 84086   💬 25

EM043 » Optical Continuous Signal Reflectometer

Description

Today commercial OTDR(Optical Time Domain Reflectometer) looks like classical pulse radar systems. They send high energy radio or lights pulse and measure reflection from car, aircraft or fiber optic defects. In this project we attempt realize continuous-wave radar concept for fiber optic monitoring system.

Demo Video

  • URL: https://youtu.be/AW0CwieZ1Y4

  • Project Proposal

    1. High-level Project Description

    Nowadays, operators use thousands of kilometers of fiber optic cable, which is used to organize backbone channels and "last mile" channels to provide access to the Internet and corporate networks for end users.

    At the present day, industrial OTDRs are pretty expensive. The main reason is that lasers with high peak power are used as the source of light, highly sensitive photodetectors with a large dynamic range as receivers and high-speed 14/20-Bit ADC for measuring backscattering. As a result, industrial OTDRs have high level of spatial resolution and minimize the time of measurement. But for many applications it is enough to have devices with more modest characteristics.

    In our work, the possibility of using low-cost laser sources and receivers is considered, also it is not planned to use expensive ADCs to obtain information about defects in an optical fiber.

    2. Block Diagram

    After several experiments, the final block diagram of device looks like this:

    Here are some components, that are used in the device:

    3. Intel FPGA Virtues in Your Project

    It should be noted that the main functions of our device can not be realized without using FPGA. Such functions as:

    • Recording of signals with precision of 1 ns.
    • Accumulation of measurement results. It means that for the time of 10ns you need to read the average value from memory, add it to the current value and save it to the memory.

    The ARM allowed us to show the results in the real time and we did it very easily.

    4. Design Introduction

    The information below shows some main principles of work of OTDR. If you need more information, you should read JDSU, “Reference Guide to Fiber Optic Testing”.


    A schematic diagram showing OTDR technology.

     


    A typical OTDR trace.

    Rayleigh Scattering: typical Rayleigh backscatter coefficient -80 dB (1ns pulse width). As result, the OTDR detector functions at extremely low optical power levels (as low as 100 photons per meter of fiber).
    Fresnel Reflection: up to 4% (-14dB). 
    The following table provides the typical reflectance values for a fiber optic connection or break.
    Glass-to-air                      -14 dB
    PC-to-PC connector         -35 to -50 dB
    APC-to-APC connector    -55 to -65 dB

    In our project, we limit ourselves to registering Fresnel reflection from optical fiber defects.

    5. Function Description

     

    TOSA - transmitter optical sub-assembly. The TOSA consists of a laser diode and monitor photodiode.
    ROSA - receiver optical sub-assembly. The ROSA consists of a photodiode and Transimpedance Amplifier.

    A typical schematic SFP (receiving path).

    Contain Transimpedance Amplifier (TIA - ADN2880) and Limiting Post Amplifier (LA - ADN2890)

    The voltage amplifier stage provides gain and converts the single-ended input to differential outputs. The DC cancellation circuit uses low-frequency feedback to remove the DC component of the input signal. This feature centers the input signal within the transimpedance amplifier’s linear range. As result this combination looks like 1-bit ADC for small signal.

    {\displaystyle \sigma ={\sqrt {{\frac {1}{n}}\sum _{i=1}^{n}\left(x_{i}-{\bar {x}}\right)^{2}}}} 
    xi = 1 or 0 => σ < 1

    σmean = σ / √N < 1 / √N

    Usually this technique is called oversampling.

    6. Performance Parameters

    Johann Carl Friedrich Gauss was born on 30 April 1777 in Brunswick (Braunschweig), in the Duchy of Brunswick-Wolfenbüttel (now part of Lower Saxony, Germany), to poor, working-class parents...

    7. Design Architecture

     

     

     



    25 Comments

    Denis
    Very interesting idea. Are there any changes to the project? Can I contact you by mail?
    🕒 Feb 28, 2019 10:03 AM
    Euclides Chuma
    Dear,
    Very interesting project. You have any progress?
    Best regards
    🕒 Jul 19, 2018 07:19 PM
    EM043🗸
    Hi
    Any additional information will be available no earlier than October. Sommerferien! :-)
    https://hackaday.io/project/159904
    Regards
    🕒 Aug 06, 2018 10:57 AM
    Pedro Miguel Baptista Machado
    This is an interesting and challenging project. There is no results and discussion and future work sections. Therefore, it is not possible to infer what was the outcome of this project.
    🕒 May 28, 2018 09:21 AM
    EM043🗸
    Hi, Pedro. Thank you for taking the time to review our project. In fact, our project is too simple in terms of its implementation in the FPGA. Same simple as one bit :-)
    But at present, we have focused on optimizing the analog part of our design. The receiving path of the SFP module was not designed to register very weak signals. As a result, we have significant problems with electromagnetic noise, flicker noise, temperature stability.
    The main goal of our project is to create a device costing less than 50$ for detecting defects in fiber-optic systems.
    At this point, the main goal was not achieved.
    🕒 May 29, 2018 12:07 PM
    Pedro Miguel Baptista Machado
    Nevertheless, you can improve it by adding the sections that I recommended. Sometimes, simplicity is required to solve a complex problem and you provide that. The target price can be archived but it is normal having the prototype costing more than that.
    Sometimes, reporting all those problems are already a contribution. Engineering means fail a lot until one gets it right. Reporting what went wrong helps others or you to get it right next time. Do not wast that knowledge, instead report it here.
    Bw
    PM
    🕒 May 29, 2018 05:07 PM
    Tariq Ziad Kanaan
    good project,
    keep gooing
    🕒 Apr 28, 2018 01:29 AM
    EM043 🗸
    Скоріше за все, наша робота не пройде в наступний раунд конкурсу, але ми маємо тверді наміри завершити наш проект. Невідомо чи залишиться можливість коментувати проекти після завершення голосування. Тому, забігаючи наперед, хочемо подякувати всім хто нас підтримав відгуками і голосами. Ми хочемо побажати всім, хто пройшов до наступного раунду, довести свої проекти до логічного завершення, висловити нашу подяку організаторам конкурсу і суддям, яким вже довелося зіткнутись з деякими труднощами, та побажати їм чесного суддівства.
    Окрема подяка всім, хто скористувався перекладачем, щоб прочитати ці рядки.
    Дякуємо! Удачі!
    🕒 Jan 30, 2018 08:04 PM
    Bogdan Belash
    Вітаю:)
    🕒 Feb 01, 2018 08:33 AM
    Ievgen Korotkyi
    Very good project! +1
    🕒 Jan 25, 2018 09:02 PM
    Bing Xia
    It is interesting, good luck
    🕒 Jan 16, 2018 06:22 AM
    EM043🗸
    Thank you for kind words.
    🕒 Jan 18, 2018 05:13 PM
    kemal eddin ahmedzad
    like it keep moving!
    🕒 Jan 14, 2018 09:38 PM
    berkay egerci
    keep going! good project and good luck !
    🕒 Jan 13, 2018 09:50 AM
    kemal eddin ahmedzad
    like it
    🕒 Jan 12, 2018 01:08 PM
    MOHAMED
    Good Project. Keep moving.
    🕒 Jan 12, 2018 02:26 AM
    Subha Sarkar
    Optics ! Amazing ..
    🕒 Jan 08, 2018 03:07 AM
    EM043🗸
    Thank you!
    🕒 Jan 18, 2018 05:16 PM
    EM043 🗸
    Similar projects:

    AP038 » Active Scanning SONAR
    http://www.innovatefpga.com/cgi-bin/innovate/teams.pl?Id=AP038

    AP050 » Compact FMCW Microwave Radar for Enhanced Vision in Robotics & Vehicles
    http://www.innovatefpga.com/cgi-bin/innovate/teams.pl?Id=AP050
    🕒 Jan 03, 2018 08:14 AM
    Sameh elmalt
    Good lucj, it's very interesting
    🕒 Jan 02, 2018 03:36 AM
    EM043🗸
    Thanks!
    🕒 Jan 18, 2018 05:17 PM
    Oleksandr Redchuk
    Very interesting and very promising. Good luck!
    🕒 Jan 01, 2018 04:55 PM
    EM043🗸
    Дякуємо за підтримку!
    🕒 Jan 18, 2018 05:17 PM
    damar cık
    hmmm interesting
    🕒 Dec 31, 2017 06:23 PM
    EM043🗸
    Thanks!
    🕒 Jan 18, 2018 05:16 PM