Laser 2000

Optical Wavelength Meter

Two versions of the 238 Optical Wavelength Meter are available. The model 238A is the most precise, providing an accuracy of ±0.3 pm. For less exacting test requirements, the model 238B is a lower-priced alternative with a wavelength accuracy of ±1.0 pm. Continuous calibration with a built-in wavelength standard ensures the utmost confidence in the test results.

Bristol Instruments

238 Series Optical Wavelength Meter

Wavelength measurement from 700 to 1650 nm

  • Wavelength accuracy as high as ± 0.3 pm
  • Continuous calibration with built-in wavelength standard
  • Measurement confi dence level ≥ 99.7%
  • Traceable to NIST standards
  • Power measured to an accuracy of ± 0.5 dB
  • Broad operational range of 700 to 1650 nm
  • Measurement rate of 15 Hz
  • Convenient touch-screen display reports measurement data in a variety of formats
  • Interfacing via SCPI using USB, Ethernet, or GPIB
  • Rugged design for manufacturing environments
  • 5-year warranty covers all parts and labour


The 238 Series Optical Wavelength Meter from Bristol Instruments is designed for the precise wavelength characterisation of tunable transmitter lasers, DFB lasers, and VCSELs used in applications such as fibre optic communications, data storage, and 3D sensing. Features such as reliable accuracy, broad wavelength coverage, straightforward operation, and rugged design satisfy the needs of both the R&D scientist and the manufacturing engineer.

Operation of the 238 Optical Wavelength Meter is straightforward. The optical signal enters the model 238 through an FC (UPC or APC) fibre optic connector on the front panel. A convenient front panel touch screen controls the 238 system and displays the measured wavelength and power. The measurement data can also be sent to a PC using a library of SCPI commands via standard USB or Ethernet interface, or an optional GPIB interface. The rugged design of the 238 Optical Wavelength Meter provides long-term reliable operation that is backed by a five-year warranty covering all parts and labour.

Model 238A 238B
Optical Signal [1] CW Only
Range 700 – 1650 nm (182 – 429 THz)
Accuracy [2], [3] ± 0.2 parts per million (± 0.3 pm at 1550 nm) ± 0.65 parts per million (± 1.0 pm at 1550 nm)
Repeatability [4], [5], [6] ± 0.03 parts per million (± 0.05 pm at 1550 nm) ± 0.1 part per million (± 0.15 pm at 1550 nm)
Calibration Continuous – built-in stabilised single-frequency HeNe laser Continuous – built-in standard HeNe laser
Display Resolution 0.00001 nm 0.0001 nm
Units [7] nm, cm-1, THz
Calibration Accuracy ± 0.5 dB (± 30 nm from 1310 and 1550 nm)
Linearity [6] ± 0.3 dB (700 – 1600 nm)
Polorisation Dependence ± 0.5 dB (700 – 1600 nm)
Display Resolution 0.01 dB
Units dBm, mW, μW
Optical Input Signal
Maximum Bandwidth [8] 1 GHz (8 pm at 1550 nm) 10 GHz (80 pm at 1550 nm)
Sensitivity [6], [9] 1000 – 1650 nm: -25 dBm (3 μW)
700 nm: -10 dBm (100 μW)
Maxiumum Power + 10 dBm (displayed level), + 18 dBm (safe level)
Return Loss 35 dB
Measurement Rate (Time)
15 Hz (0.07 s)
Inputs / Outputs
Optical Input 9/125 μm single-mode fibre (FC/UPC or FC/APC)
Instrument Interface Library of commands (SCPI) via USB 2.0, Ethernet, and optional GPIB
Warm-Up Time < 15 minutes None
Temperature +15°C to +30°C (-10°C to +70°C storage)
Pressure 500 – 900 mm Hg
Humidity ≤ 90% R.H. at +40°C (no condensation)
Dimensions & Weight
Dimensions (H x W x D) 89 mm x 432 mm x 381 mm
Weight 7.65 kg
Power Requirements
90 – 264 VAC, 47 – 63 Hz, 80 VA max
5-year (parts and labour)
[1] Maximum amplitude noise of 1%.
[2] Defined as measurement uncertainty, or maximum wavelength error, with a confidence level of ≥ 99.7%.
[3] Traceable to an NIST standard (SRM 2517a).
[4] For 238A, standard deviation for a 10 minute measurement period.
[5] For 238B, standard deviation for a 1 minute measurement period. Maximum long-term measurement variation < ± 0.4 ppm.
[6] Characteristic performance, but non-warranted.
[7] Data in units of nm and cm-1 are given as vacuum values.
[8] Bandwidth is FWHM.
[9] Performance at other wavelengths can be determined from graphs that are available upon request.

Bristol Instruments reserves the right to change the specifications as may be required to permit improvements in the design of its products. Specifications are subject to change without notice.

238 Series Datasheet
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238 Series

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