ACES Int'l

Secrets & Tips

for Fiber Optics (Page 2)

    by Sam Starklauf

The Traditional Approach

Most technicians are familiar with the standard or traditional test equipment used to ensure that the customer’s acceptance criteria are met. For visual inspection a 200X to 400X inspection Microscope such as the Noyes OFS 300 can be used to inspect connectors that become parts of fiber optics cables, patch cords, or test jumpers.

For example they can be used to examine the endface/profile of the connector during the polishing process to ensure not only an acceptable end product but one that is consistently reproducible no matter what the level of training or experience. They may also be used to check the endface profile of the bare fiber to be spliced.

Optical power measurements can be performed using a standard Noyes Optical Loss Test Set (such as an OLS5/OPM5 or the OLS6/OPM6). Three standard power measurements that can be performed on a completed fiber optic cable or assembly are continuity, link or insertion loss (also referred to as attenuation), and return loss also known as back reflectance. The OLTS should be capable of performing these tests at all required operating wavelengths. Fiber optics technicians and installers in today’s technical organizations commonly use methods and equipment described above. The alternative method described below is not quite so commonly used or even thought of by most organizations.

The Alternative Approach

The second or alternative approach utilizes DAQ’s, light detectors and frame grabber boards in a standard personal computer to replace the traditional fiber optics test equipment. Such an approach is almost never utilized or even thought of when the purchase of fiber optics test equipment is being considered except in state of the art research labs. This is a shame for test equipment built around such systems have many advantages. They are easily reconfigurable, lends itself readily to automation to lower costs and reduce test times, and increased accuracy. Such advantages are beneficial in both production and assembly of fiber optics components and their installation into fiber optics networks. Such a system lends itself easily to the development of fiber optics inspection and testing techniques and is readily calibrate-able to provide values traceable to NIST.

To meet these objectives, I would like to develop two follow-up articles and their associated applications. The first application I would like to illustrate is a computer based test system that would be used to measure and test optical power of completed optical components and cable assemblies. The system would not only be useful as a training aid to teach test techniques in an advanced fiber optics inspection and test course but could be used to test passive fiber optic components in a DWDM system. It would also allow you to document common test parameters and their test result to complete your system documentation requirements of the customer.

Some test parameters that can be incorporated in such a system are:

1. the amplitude or optical power itself
2. insertion losses (attenuation)
3. return loss for wavelengths under test
4. a simple continuity test
5. optical return loss
6. bandwidth or spectral width
7. channel isolation and crosstalk
8. Optical signal to noise ratio

The second application that I would like to develop is an inspection and test system used to view and define/document typical cable and connector inspection measurements such as core/cladding dimensions, circularities, concentricity and to detect surface anomalies and defects. In addition it could be used to examine and troubleshoot the connectorization polishing process to ensure the quality of the endface by an organizations technicians and installers. Finally such a system could be used to examine the cleaves made to the bare fiber during the splicing process used to connect two fibers/bundles by the technicians/installers to meet customer/splice equipment criteria and as a training aid to qualify an organization technicians/installers.

For my purposes, the key to assembling a basic fiber optics inspection and test system is to utilize the hardware and software tools available from National Instruments. Not only do they offer excellent hardware and software products but offer additional aid in terms of customer solutions and a resource library of program developed and tested to support their customers in the development of specific applications for their products. Expert assistance is also available by either telephone or email. With this type of support your system needs and development time is cut down tremendously and allows you to put your applications to work almost immediately.

A key component for both applications is the National Instruments software package LabVIEW. LabVIEW is an extremely powerful package that can be used with a variety of bus structures including the standard PCI bus, GPIB, and serial RS-232/485. It can perform statistical analysis such as averaging, min/max, standard deviations, chart data, and be used to spot data trends. It can also be used to perform data logging to disk or to a database as required.

The bottom line is that LabVIEW can be used in a variety of applications including research and development, training, manufacturing, production, and testing of optical components and assemblies. LabVIEW is available for most platforms and can be used with the operating system of your choice. With this in mind I will use for my applications, to be developed here, a currently available system using Windows 98 as my operating system of choice.

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