Numerical Aperture Conversion Adapter (DISCONTINUED)

Notice: This product was discontinued on Jun 10, 2022. See this replacement product:

The 735383-A001 and A002 are unique adapters that reduce the numerical aperture (NA) of an optical fiber to half and is only applicable to the free space optical input structure on the Yokogawa AQ6370 series optical spectrum analyzers.

What is the numerical aperture of an optical fiber?

What is meant by 'numerical aperture?'  The numerical aperture is the range of angles at which an optical fiber can transmit its beam. It's related to refraction and the beam spread angle.

Numerical Aperture Formula

Numerical Aperture (NA)=n×sin(µ) or n×sin(α)

Applicable fiber: Multimode fiber (GI50/125µm and GI62.5/125µm)

Unique adapter for the Yokogawa free space input


NA ConversionAdapter
NA Conversion Adapter
NA Freespace
Free Space input of AQ6370 Series

How It Works

The NA Conversion Adapter halves the numerical aperture (NA) of a connected fiber.

NA How It Work

Benefits of the NA Conversion Adapter


Better dynamic range (SNR) for passive component testing
The use of a multimode fiber causes a high coupling loss with a broadband light source so that high output power cannot be expected, and the direct output of such a fiber is reduced in the Monochromator due to the NA restriction.
By attaching the adapter to the end of a multimode fiber, the optical spectral level of a broad band source increases about 5 dB on the OSA.
  NA BetterDynamicRange


Better level stability for active device testing
With the direct output of multimode fiber, there are cases where the measured power level becomes unstable due to dynamic speckle noise caused by modal interference.
The NA conversion adapter can resolve the above issue and improves the level measurement stability by efficiently coupling the output beam with the Monochromator.
 • Level Fluctuation    • Ripple on LED Spectrum
NA Level Fluctuation   NA Ripple
DFB-LD Spectrum (GI 50/125 µm)    EE-LED Spectrum (GI 50/125 µm)


Product Code 735383-A001 735383-A002
Applicable Fiber SMF, GI50/125um SMF, GI50/125um, GI62.5/125um
Wavelength Range 350 to 1700nm (typ.)
NA Conversion Ratio Approx. 1/2 
Applicable OSA Models AQ6370 series Optical Spectrum Analyzers
Note: the wavelength restriction applies to the AQ6375 
Note: Wavelength resolution doubles when the NA conversion adapter is used.

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