The photonics community needs a method for very high dynamic range measurements of optical fiber, waveguide and other optical components. Advances in DWDM technology, increased deployment of standard fibers, and the growing development of specialty fibers all require more accurate characterization. Until now, these high dynamic range measurements of irradiant light flux have been very difficult to obtain. Photon has the solution: our new goniometric radiometer, the LD 8900HDR Far-Field Profiler.

Measurement Parameters
The the LD 8900HDR Far-Field Profiler uses goniometric methodology to measure true 3-dimensional profiles of optical components with up to 93 dB dynamic range. All measurements are taken with the emitting fiber, planar waveguide, laser diode or LED inserted directly into the center of the instrument's radial measurement area. For optical fiber, the far-field distribution pattern is acquired without bending the fiber. Bending the fiber can cause analysis and reporting inaccuracies. The 2D parameters measured for optical fiber are:

• Mode Field Diameter (MFD) -- used to evaluate losses due to mismatch at con-nections of fibers and fiber components.
• Effective Area (A_eff) -- used to assess non-linear effects.
• Numerical Aperture (NA) -- a measure of the angular width of the fiber output. NA is equal to the sine of the half angle (sin q/2) at a specified percentage of the peak value.

The Model LD 8900HDR analysis software calculates these optical fiber parameters from the far-field profile, the method described in the TIA/EIA FOTP-191 standard for MFD requiring a minimum of 50 dB for proper measurement. The TIA/EIA FOTP-132 standard for A eff requires a minimum of 50 dB for proper measurements as well.

This wider dynamic range provides greater signal-to-noise detail in the tails of the far-field pattern. Real-time data gathering and reporting of sample optical fibers or other sources is valuable for manufacturing and quality assurance evaluation.

Hardware and Computer
The LD 8900HDR is a modular system that allows either one-dimensional or three-dimensional measurements. The 3D module is easily exchanged with the 1D hardware, and the system can be purchased with the 1D hardware, the 3D hardware or both. There are specially designed fiber mounting clips available for both the 1D and 3D configurations with a specially modified fiber cleaver and clip that guarantees proper fiber alignment. In addition, custom mounting devices are available for high dynamic range measurements of waveguides, laser diodes and LEDs.

The controller comprises the PC microprocessor, data acquisition card, scan-control card and LD 8900HDR acquisition and analysis software. A reference calibration standard (NIST traceable), 1310 nm, 0 dBm LD Light Source is also available. This is the measured reference at the time of original manufacture that can be used for unit verification by the user at a later date. For high dynamic range measurements in the visible spectrum, a silicon detector can be substituted with a spectral range of 320-1100 nm and even higher 103 dB dynamic range. Maximum light source unit size for direct measurements is approximately 12.7 mm by 12.7 mm. In the 3D configuration the LD 8900HDR includes the 3D Motion Control Module and is capable of full 3D measurements with up to 200 azimuthal planes through the source.

Close-up of Fiber Mount Measurement results from Model FO 8400XL 3D

2D Single-Scan Data 3D Multi-Scan Data

LD 8900HDR Specifications: