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A simple OTDR SOR file parser

Project description

The SOR (“Standard OTDR Record”) data format is used to store OTDR (optical time-domain reflectometer ) fiber data. The format is defined by the Telcordia SR-4731, issue 2 standard. While it is a standard, it is unfortunately not open, in that the specifics of the data format are not openly available. You can buy the standards document from Telcordia for $750 US (as of this writing), but this was beyond my budget. (And likely comes with all sorts of licensing restrictions. I wouldn’t know; I have never seen the document!)

There are several freely available OTDR trace readers available for download on the web, but most do not allow exporting the trace curve into, say, a CSV file for further analysis, and only one that I’ve found that runs natively on Linux (but without source code; although some of these do work in the Wine emulator). There have been requests on various Internet forums asking for information on how to extract the trace data, but I am not aware of anyone providing any answers beyond pointing to the free readers and the Telcordia standard.

Fortunately the data format is not particularly hard to decipher. The table of contents on the Telcordia SR-4731, issue 2 page provides several clues, as does the Wikipedia page on optical time-domain reflectometer.

Using a binary-file editor/viewer and comparing the outputs from some free OTDR SOR file readers, I was able to piece together most of the encoding in the SOR data format and written a simple program (in Python) that parses the SOR file and dumps the trace data into a file. (For a more detailed description, other than reading the source code, see my blog post).

Presented here for your entertainment are my findings, in the hope that it will be useful to other people. But be aware that the information provided here is based on guess work from looking at a limited number of sample files. I can not guarantee that there are no mistakes, or that I have uncovered all possible exceptions to the rules that I have deduced from the sample files. use it at your own risk! You have been warned!

The program was ported over from my original pubOTDR written in Perl. To parse an OTDR SOR file, run the program as

pyOTDR.py myfile.sor

where “mfile.sor” is the name (path) to your SOR file. A OTDR trace file “myfile-trace.dat” and a JSON file “myfile-dump.json” will be produced. You can also output the results as an XML file “myfile-dump.xml” with:

pyOTDR.py myfile.sor XML

There is also a Ruby version (rbOTDR), a javascript/node version(jsOTDR), and a Clojure version (cljotdr); the Clojure version may be of interest to people looking for a Java version, since Clojure runs on top of a Java Virtual Machine (JVM).

Install

This program requires python 2 or python 3. To install dependencies, run

pip install -r requirement.txt

I recently reorganized the whole package to submit to PyPI (Python Package Index). You should now be able to install the whole thing with

pip install pyOTDR

This should create an executable called pyOTDR that is ready to use.

Docker

There is a docker image that you can download with the command

docker pull sidneyli/pyotdr:latest

If you would like to build the docker image yourself, a docker file (Dockerfile) is provided to help you test this program. In the top level directory, type the command

make docker-build

or type the command

docker build . -t sidneyli/pyotdr:latest

to build the docker image. It will take a while to download the base image and compile. If all goes well, it should successfully build a new docker image sidneyli/pyotdr:latest. You can check with the command:

docker images

once the build is completed. You can now run the command

make docker-run

or type the docker command:

docker run -ti --rm -v $HOME:/data sidneyli/pyotdr:latest /bin/bash

to spin up an instance of the docker image. This will start a command shell for you to run the pyOTDR.py program. The docker command above will mount your home directory to the /data folder inside the docker instance. The command pyOTDR.py (installed as /pyOTDR/pyOTDR.py) will be in your execution path. The docker instance removes itself when you exit the instance.

(Last Revised 2018-01-12)

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