Advantest R3172 Spectrum Analyzer 9KHz - 26.5GHz

The advantage of the old 6581 is that there is a reverse enginered schematics available, if needed for a repair. 

As a downside the displays are often dim and a replacement is a bit tricky.

A know weak point for the 6581 is the rather large current spike from AZ switching - this can be an issue with some signal sources. 

Another point is that ACAL may not be fully accurate for the highest resistor ranges. 

So the specs there may be a bit overly optimistic. 

Quite a few of the old meters also have a relay power saving mode not working right 

that can cause some thermal EMF error that can effect the lower voltage ranges - this is fixable at least.

The 6581T tends to have a rather poor factory calibration that causes quite some INL error 

- so while the ADC is essentially the same as with the full version, the linearity is not that great for the T version.

There may be ways to correct this, but it is extra effort and may need extra instruments (e.g. cal source).

Brief Description

The Q8383 is an advanced spectrum analyzer (Advantest) with a two-pass monochromator and very low polarization dependence.

Thanks to a special method, values of ±0.05 dB are guaranteed, with typical values as low as 0.02 dB.

Together with the high accuracy of the resolution bandwidth, the Q8383 can be used to perform precise power measurements.

All of these features make the Q8383 an ideal measurement instrument for erbium-doped fiber amplifiers (EDFAs).

By simply comparing the signal at the input of the amplifier with the signal at the output of the amplifier, 

special measurement functions can be used to determine the noise figure, gain and spontaneous emission.

Of course, all these functions are also of great advantage when measuring laser diodes, light emitting diodes and other light sources.

The curve fitting function directly displays electroluminescence characteristics by fitting a Gaussian distribution to the emission spectrum.

This is very useful for measuring Erbium Doped Fiber Amplifiers (EDFA) and Light Emitting Diodes. 

A special feature for pulsed light allows measurements of fiber optic rings and soliton transport systems. 

Internal or external triggering is possible.

Measurement time is 0.8 seconds for a span of 200 nm and varies with the span.

Broadband light sources with a resolution of 5 nm have the highest sensitivity, 

while narrowband light sources (lasers) can be reliably analyzed down to the noise level even with a narrow resolution bandwidth.

The normalization function combined with the white light source allows direct measurement of transmission and loss characteristics of filters and fibers.

Operation

In addition to amplifier analysis, a variety of display modes are available, such as

- Overlay display,

- Comparison with memory contents,

- Display of two independent graphs (split screen),

- Power meter function,

- Use of multiple markers,

- Normalized and direct readout of transmission loss and

- Automatic bandwidth analysis (e.g. measurement of half-value widths based on RMS and envelope methods),

- Curve fitting over the IEC/IEEE bus and many other features facilitate operation of the analyzer and simplify analysis.

Measurement time is 0.8 seconds for a span of 200 nm and varies with the span.

Broadband light sources with a resolution of 5 nm have the highest sensitivity, 

while narrowband light sources (lasers) can be reliably analyzed down to the noise level even with a narrow resolution bandwidth.

The normalization function combined with the white light source allows direct measurement of transmission and loss characteristics of filters and fibers.

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