A very important test of tunable lasers is accurate wavelength measurement and calibration. With the continuous increase of communication channels, from the first 40 waves to the current maximum of 800 waves, because each wavelength needs to be calibrated by a wavelength meter, fast and accurate wavelength measurement is more critical than ever.

FWM8612 is based on Fizeau interferometer technology, which combines a temperature stable control interferometer, a multi-stage composite interference cavity and a linear array CCD detector. Unlike the traditional ordinary wavelength meter based on Michelson interferometer, fwm8612 adopts all solid-state structure and optical design of non mechanical moving parts, which enables it to ensure very high measurement accuracy (0.5pm) and ultra-high measurement rate (up to 1kHz wavelength brushing rate). Combined with external triggering and fast power detection functions, fwm8612 becomes the best choice for accurately observing the transient changes of wavelength and power synchronization.

Semight Instruments FWM8612 fast wavelength meter

Main features of FWM8612

• high wavelength accuracy: ± 0.33ppm (typical value: ± 0.5pm), superior to ordinary wavelength meters such as Bristol (USA) 438b / Yokogawa (Japan) aq6150 / keysight (USA) 86120b / C series, and equivalent to the 0.3pm accuracy of the industry's highest precision wavelength meter, which can be used for wavelength calibration and measurement;

• 0.1pm/12.5mhz wavelength resolution;

• all solid state structure, optical design of non mechanical moving parts, fast test speed: 1kHz refresh rate, suitable for transient wavelength and power test, greatly reducing the test time of itla, DBR and coherent communication modules;

• suitable for fast wavelength testing of itla and tunable lasers;

• it supports broadband mode and can test the accurate wavelength measurement of 96gbaud modulated optical signal;

• support drift test and maximum and minimum value display;

• support external or internal triggering, use FPGA to drive wavelength / power synchronous acquisition, and cooperate with SMU precision source meter to conduct synchronous test to ensure the accuracy of collected signals;

• the SCPI standard instruction is compatible with the corresponding instruction set of keysight / Yokogawa and other manufacturers;

• suitable for wavelength power testing of various optical devices such as COC / Tosa / module.

Application scenario 1: single sampling mode

In the common single sampling mode, the sampling rate of FWM8612 wavelength meter of lianxun instrument can be as high as 200Hz, which is 20-100 times that of the common multi wavelength based on Michelson interferometer, with power accuracy < 0.5dB and repeatability < 0.02dB.

FWM8612 single sampling mode test results

Application scenario 2: internal trigger sampling mode 

Semight Instruments fwm8612 has a built-in trigger signal generator, and its fast measurement function. As shown in the figure below, the internal trigger 1000Hz is used to measure the switching period and stability of ordinary mechanical optical switch, and the transient wavelength and power information of the adjustable laser can be observed.

FWM8612 internal trigger sampling mode

Application scenario 3: external trigger sampling mode

The FWM8612 fast wavelength meter of lianxun instrument supports 5V TTL trigger level, and the sampling rate is up to 1000Hz external trigger. It can synchronously measure the scanning spectrum of the adjustable laser, the modemap scanning and channel calibration of the adjustable laser, and the wavelength power of the pulse laser is the same as the monitoring.

FWM8612 external trigger sampling mode

FWM8612 test adjustable laser mode map

Application scenario 4: Broadband working mode

In general, the wavelength calibration and test of tunable laser are carried out without modulation. Either the multi wavelength meter based on Michelson interferometer or the fast wavelength meter based on fisso interferometer of lianxun instrument are more suitable for the accurate wavelength measurement of narrow linewidth laser. However, in some special occasions (equipment under test), it is necessary to perform wavelength test under the condition of modulated signal. We know that high-speed modulation will broaden the spectrum of the original narrow linewidth laser (the linewidth is usually at kHz ~ MHz) (96Gbaud modulation signal, the spectrum is broadened to 96GHz), as shown in the figure below, which makes accurate wavelength measurement a new challenge.

Unmodulated laser signal spectrum (left) laser spectrum broadening after modulation (right)

As the industry standard, the wavelength accuracy indexes of keysight 86122c in the United States and Yokogawa aq6151b in Japan can only guarantee the linewidth < 2.5GHz. For signals with higher modulation bandwidth, the wavelength accuracy cannot be guaranteed. However, in order to meet the accurate measurement of the wavelength of the broadband modulation signal, FWM8612 has further optimized on the original basis, and finally realized the accurate measurement of the wavelength of the 400G qam16 (96Gbaud) signal. As shown in the figure below, Compared with the keysight 86122c in the United States, it has achieved better stability (blue is the test result of fwm8612, orange is the long-term stability test result of keysight 86122c, and the peak value is higher than FWM8612).