YOKOGAWA AQ6375B Long Wavelength Optical Spectrum Analyzer 1200 – 2400 nm


High Performance LONG WAVELENGTH
The AQ6375B is a bench-top optical spectrum analyzer covering the long wavelengths, 1200 to 2400 nm, with the added benefits of gas purging input ports / output ports, a built-in cut filter for high order diffracted light, and a novel double speed mode which increases the sweep speed up to 2 times compared to the standard sweep mode.

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The Yokogawa AQ6375B has been designed to increase productivity of R&D and Production personnel.

The software has pre-installed analysis functions for the most common optoelectronic (passive and active) devices. The automatic calculation of the major parameters of the device under test will contribute to its fast characterization.

Moreover, the AQ6375B has the capability to be programmed to perform automatic measurements while controlling other lab equipment.

New Functions

Data logging function 

Records analysis results such as distributed feedback laser diode (DFB-LD) analysis data and multi-peak measurements at up to 10,000 points per channel with time stamps.

Smoothing function

Reduces the noise on the measured spectrum.

Built-in analysis functions to increase your testing efficiency

Spectrum Width Analysis

You can display the spectrum width and center wavelength using the following 4 types of calculation:

  • THRESH method
  • ENVELOPE method
  • RMS method
  • PEAK RMS method

Notch Width Measurement

With this function it is possible to measure pass bandwidth / notch width from the measured waveform of a filter with V-type or U-type wavelength characteristics.

Light Source Analysis

Light source parameters can be analyzed from the measured waveform of each type of light source among DFB-LD, FP-LD and LED.PMD Measurement

It is possible to measure the Polarization Mode Dispersion (PMD) of a DUT (such as an optical fiber) by using the instrument in combination with an Analyzer, Polarization Controller, Polarizer, and an Amplified Spontaneous Emission (ASE) light source, High-output LED light source, or other wideband light source.

WDM Analysis

With this function it is easy to analyze WDM transmission signals. You can also measure OSNR of a DWDM transmission system with 50 GHz spacing. Measurements of WDM signal wavelength, level, wavelength interval, and OSNR can be made collectively on up to 1024 channels, and the analysis results can be displayed in a data table.

Optical Amp Analysis

Gain and Noise figure measurements can be made on signal light waveforms going into optical amplifiers, as well as light leaving the optical amplifiers.

Optical Filter Characteristics Measurement

Optical filter characteristics can be measured from the measured waveforms of the light, from source, going into optical filters, as well as from the measured waveforms of light being output from optical filters. Analysis can be performed not only on optical filters with one mode, but also multimode filters (e.g WDM Filters).

Measurement of Level Fluctuations in Single-Wavelength Light

This function is used to measure changes over time in the level of a specific wavelength level. The sweep width is set to 0 nm, and measurement of the single-wavelength light is taken. The horizontal axis is the time axes. It is useful for purposes such as optical axis alignment when a light source is input to an optical fiber.

Template Analysis

The template function compares preset reference data (template data) with a measured waveform. In addition, if a function for displaying the target spectrum (target line) on the measurement screen is used, the target spectrum can be referenced while adjusting the optical axis of an optical device.

Go/No Go Judgment

The Go/No Go test function compares the active trace waveform against reference data (template data) preset by the user, and performs a test on the measured waveform (Go/No Go test).
This function can be used effectively in situations such as pass/fail tests on production lines.

Analysis between Line Markers / in the Zoom Area

The instruments perform the analysis of the signal contained into boundaries selected by means of line markers or zoomed area.

Building Automated Test Systems


The AQ6375B is equipped with GP-IB, RS-232, and Ethernet (10/100Base-T) interfaces, which can be used for remote access and control from an external PC to build automated test systems. Built-in Macro Programming function is also available to implement simple auto test programs on the unit it self.


The standard remote commands of the AQ6375B are compatible with SCPI, which is an ASCII text based standard code and format conforming to IEEE-488.2.


The AQ6375B supports proprietary remote programming codes of Yokogawa’s best selling AQ6317 series for users to easily upgrade from their current automated test environment.


Macro programming enables user to easily create test procedures by recording the user’s actual key strokes and parameter selections. An external PC is not required because the macro program can also control external equipment through the remote interfaces.
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LabVIEW® DRIVER available

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YOKOGAWA AQ6375B Key feature summary:

  • Long wavelength range: 1200 to 2400 nm
  • Gas purging ports to reduce water vapor effects
  • Built-In cut filter for high order diffracted light
  • Double Speed Mode to further enhance fast measurement speed
  • High sensitivity down to -70 dBm
  • High resolution to 0.050 nm
  • Wide close-in dynamic range (55dB)
  • Fast auto-calibration
  • Free space optical input for maximum flexibility, low maintenance, and high reliability
  • Applicable to single-mode and multimode fibers
  • Excellent performance for environmental gas sensing Laser Spectroscopy
  • Indispensable tool for R&D and manufacturing of optical devices in the wavelength range from telecom band to 2.4μm

New Features

Purge feature

Due to the high resolution and sensitivity of the YOKOGAWA AQ6375B, it can actually detect the presence of water molecules in the air. The water vapor is detected in the upper Near-IR wavelength region and could overlap with or mask the spectral characteristics of the actual device under test in that particular region.

By continuously supplying a pure purge gas such as nitrogen to the monochromator through the ports on the back panel, the AQ6375B can reduce the influence of water vapor absorptions and provide more reliable and accurate measurements than ever before.

Built-in cut filter for high order diffracted light

Due to the diffractive technology used, the monochromator in some circumstances could generate high order diffracted light, which appears at wavelengths equal to the integral multiple of input wavelengths.

By cutting incoming light below 1150 nm with the built-in filter, the AQ6375B drastically reduces the influence of high order diffracted light on the measurement. Thus, the measured data are always reliable and replicate the real signal under test.

Double speed mode

Increases the sweep speed up to 2 times compared to the standard sweep mode, with only a 2 dB penalty to the standard sensitivity value.

Long Wavelength Range: from 1200nm to 2400nm

The YOKOGAWA AQ6375B covers not only the wavelength span used in communications, but also the 2µm region which is used for environmental sensing, medical, biology and industrial applications.

High Sensitivity: down to -70dBm

The AQ6375B can measure optical power from +20dBm down to -70dBm thanks to its high-dynamic and very low noise components and circuits used for photo detection. This enables precise measurements of both high power and low power sources.

Measurement sensitivity can be chosen among 7 values according to the measurement speed required by the specific test to be performed.

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The spectrum of a white light source (yellow) and the background noise of AQ6375B (purple)

High Resolution & Wide Dynamic Range

The YOKOGAWA AQ6375B uses a double-pass monochromator structure to achieve high wavelength resolution (0.05 nm) and wide close-in dynamic range (55 dB). Thus, closely allocated signals and noise can be separately measured.

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Measured HeNe Laser (1523 nm), Close-in Dynamic range: @ peak±0.8 nm

High speed Measurement


High Speed Sweep

With a proprietary sweep technique the AQ6375B achieves a much faster sweep speed than conventional measurement systems, which use a monochromator. Max. sweep time is only 0.5 sec. for 100 nm span.

Fast command processing and data transfer

Applying a fast microprocessor, the AQ6375B achieves very fast command processing speed and Ethernet interface provides up to 100 times faster data transfer speed than GP-IB.

Fast auto-calibration

The YOKOGAWA AQ6375B has a built-in reference light source for wavelength calibration and optical alignment of the monochromator components, allowing it to deliver always-accurate measurements.
The calibration and alignment process takes less on the unit take than 2 minutes and is fully automatic.
NOTE: The wavelength calibration can also be performed by using an external reference source.

Free-Space Optical Input

The AQ6375B uses a free-space optical input structure, i.e. no fiber is mounted inside the instrument.

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This smart solution is:

  • WORRY-FREE, as no internal fiber can be scratched or get dirty
  • MAINTENANCE-FREE, as no internal fiber has to be cleaned
  • VERSATILE, as the instrument accepts both /PC and /APC connectors
  • DUAL PURPOSE, as the instrument accepts both Single-Mode and Multi-Mode fibers without being affected by the high insertion loss from MM-SM fibers matching


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