The spread of next-generation 5G mobile communications and cloud services is increasing data traffic and network speeds, and capacities are expected to be increased using faster 10G, 100G, and 400G bit rates. Infrastructure operators are strengthening optical fiber circuits as well as increasing the speed of TRx equipment in data centers. These trends are expected to lead to rapidly increasing demand for optical devices used by high-speed communications equipment. To meet this demand, optical device makers require accurate instruments for measuring many different types of optical devices at high volumes on production lines.
With its excellent performance, high speed, and support for many different types of optical device, Anritsu’s Optical Spectrum Analyzer MS9740B is the ideal measurement solution for customers requiring secure, stable, and efficient optical spectrum tests of optical devices.
Excellent Performance
Accurate measurement of optical modules requires an optical spectrum analyzer with excellent optical performance (wavelength range: 600 to 1750 nm, minimum resolution setting: 30 pm, good wavelength accuracy, linearity, and level accuracy). Moreover, supporting both single-mode fiber (SMF) and multimode fiber (MMF) helps customers requiring tests of optical transceivers, such as SFP and QSFP modules used in optical networks, as well as tests of 850-nm VCSELs and DFB light sources, etc., built into optical transceivers.
Optical Transceiver
VCSEL and DFB-LD Evaluation
Ideal for MMF VCSEL Evaluation
With a wavelength measurement range of 600 to 1750 nm, the MS9740B covers both single-mode and multimode applications. As well as supporting wavelengths used by communications, such as 1310 and 1550-nm SMF, the all-in-one MS9740B can also measure short wavelength bands used by MMF.
Connection losses at evaluation of 850-nm band VCSEL modules are minimized by input to MMF to assure efficient measurement of device characteristics while maintaining good optical sensitivity and high-speed sweeping at level and SMSR measurements. This supports optimum evaluation of optical devices using MMF input, such as VCSELs.
Example of Device Characteristics Evaluation
Example of 850 nm VCSEL Spectrum Measurement
Supports Optical Pulse Measurement Under Asynchronous Conditions Without Trigger Signal Input
With production of high-bit-rate LDs supporting recent deployment of high-speed networks, thermal countermeasures at LD chip production have become an issue in both communications and non-communications fields. There is increasing demand for spectrum measurement using pulsed optical input as a solution to this issue.
High-output CW LD chips suffer wavelength spectrum drift and decreased power level due to thermal effects.
Example of spectrum change due to LD chip temperature increase
Optical pulse measurement suppresses the impact of this phenomenon by adjusting the repetition frequency and Duty ratio to control the LD chip temperature.
Controlling LD chip temperature using pulse driving
However, generally, accurate measurement of an optical pulse signal requires synchronization with an input trigger signal. Unfortunately, when using this method, the slow seep speed compared to CW measurement, which does not require this synchronization, causes trigger-signal input related measurement difficulties, especially with tact times at manufacturing and inspection.
By using the MS9740B optical pulse measurement mode (Opt-020), the LD pulsed optical spectrum can be measured in about the same time as CW optical spectrum measurement under asynchronous conditions without trigger signal input. When using this mode, the important SMSR evaluation also achieves a high measurement reproducibility of ±1.4 dB*.
* With MS9740B-020.
±1.8 dB with Multimode Fiber Interface MS9740B-009 installed
Using SM fiber and DFB-LD with 1550 nm wavelength at 10 dBm peak power input, with 45 dB max SMSR and no change in polarization conditions
Pulse conditions: 5 kHz min repetition frequency and 1% min Duty, Pulse Mode enabled, 1 kHz VBW, 0.1 nm Setting Resolution, 10 nm max span, 501 sampling points, at 23C°±5°C
Supports Various Optical Modules
Measurement methods and items differ according to the type of optical module when evaluating the optical spectrum of optical devices, making an optical spectrum analyzer with measurement modes for each optical module type very convenient.
The MS9740B has various measurement applications required for evaluating active optical devices (LD-Modules, DFB-LDs, FP-LDs, LEDs, WDMs, Optical Amplifiers (NF and Gain)) and supports all-at-once measurement of key evaluation items, such as center wavelength, level, OSNR, spectrum width, etc., on production lines. Analysis results are displayed on-screen for at-a-glance confirmation by operators for fast evaluation of individual optical devices.
Applications
| Application |
Test |
| DFB-LD |
Spectrum evaluation of single longitudinal mode oscillation laser |
| FP-LD |
Spectrum evaluation of laser with multiple discrete oscillation wavelengths |
| LED |
Spectrum evaluation of wideband light source |
| PMD |
Evaluation of PMD characteristics of optical fiber cable |
Opt. Amp
Opt. Amp (Multi-channel) |
Evaluation of fiber amplifier (EDFA) Gain and NF characteristics |
| WDM |
Spectrum evaluation of WDM signal with up to 300 wavelengths (channels) |
| LD Module |
Evaluation of characteristics of optical transceivers, etc. |
| WDM Filter |
Analysis of optical bandpass filters |
DFB-LD, FP-LD, LED: Analysis of Light-Emitting Elements
DFB-LD (distributed feedback laser diode), FP-LD (Fabry-Perot laser diode), and LED (light emitting diode) measurement items can be measured all at once with easy-to-understand on-screen display for more efficient evaluation.
DFB-LD Measurements
The DFB-LD is a single-spectrum semiconductor laser diode. It is commonly used in high-speed, long-distance communications applications due to its low optical-signal wavelength variation and small optical-signal waveform deterioration. The following items are measured for DFB-LD applications.
- Peak: Peak wavelength and peak level
- 2nd Peak: Side-mode wavelength and level
- Kσ: Spectrum width using RMS method
- SMSR: Side-Mode Suppression Ratio
- Mode Offset: Offset between side-mode and peak wavelengths
- Stop Band: Offset between both-side wavelengths of peak wavelength
- Center Offset: Offset between peak wavelength and mean of both-side mode wavelengths
- σ：Standard Deviation
- ndB Width: Spectrum width at set cut level
Example of DFB-LD Test
FP-LD Measurements
The FP-LD is a semiconductor laser with multiple longitudinal oscillation modes in the spectrum. They have a wide application range for optical-disk (DVD, BD) pickups, laser printers, laser pointers, etc. The following items are measured for FP-LD applications.
- Peak: Peak wavelength and peak level
- Mean Wl: Center wavelength
- FWHM: Spectrum width measured by RMS method (2.35 σ)
- Total Power: Total power of spectrum
- Mode (dB): Longitudinal oscillation mode count
- Mode Spacing: Longitudinal oscillation mode gap
- σ: Standard deviation of spectrum measured using RMS method
Example of FP-LD Test
LED Measurements
The LED is a light-emitting element with a continuous spectrum. Due to the low power consumption and very long life, LEDs are being used recently for lighting applications and automobile headlamps. The following items are measured for LED applications.
- Peak: Peak wavelength and level
- Mean Wl (n dB): Center wavelength measured using ndB Loss method
- Mean Wl (FWHM): Spectrum half-width center wavelength
- ndB Width: Spectrum width measured using ndB Loss method
- FWHM (2.35 σ): Spectrum half-width measured using RMS method
- PkDens (/1 nm): Maximum spectrum density
- Total Power: Total power in spectrum
- Kσ: Spectrum width measured using RMS method
- σ: Standard deviation of spectrum measured using RMS method
Example of LED Test
PMD: Optical Fiber Cable Polarization Mode Dispersion Measurements
Polarization Mode Dispersion (PMD) causes the optical pulse width to become wider as optical pulses pass through optical fiber and optical parts due to differences in propagation speeds caused by two polarization modes.
The PMD measurement function measures the Differential Group Delay due to the time difference between polarization components.
Example of PMD Test
Opt. Amp/Opt. Amp Multichannel: Evaluation of Fiber Amplifier (EDFA) Gain and NF Characteristics
The Gain and Noise Factor (NF) can be calculated automatically from the optical fiber amplifier (EDFA) input optical spectrum and output optical spectrum using three built-in types of measurement method (pulse, level interpolation, and polarization nulling).
Additionally, both WDM signals and the latest IEC-recommended Opt. Amp (Multichannel) applications are supported
- Supports IEC-recommended ISS (Interpolated Source Subtraction) method for Gain and ASE analysis
- New mode for detecting noise position automatically
- Built-in Gain Variation and EDFA Output Slope analysis application
Example of Fiber Amplifier Test
WDM: Evaluation of WDM Signal Spectrum for up to 300 Waveforms (Channels)
With a wide dynamic range of better than 58 dB (±0.4 nm from peak wavelength) and a higher resolution of 30 pm, the MS9740B can be used to evaluate high-speed, large-capacity, multiplexed optical WDM signals (100 GHz, 50 GHz spacing) in a fiber cable carrying many different optical wavelengths simultaneously.
Key data for WDM signal analysis, such as center wavelength, level, SNR, etc., can be analyzed for up to 300 channels at once. Separation between channels can also be confirmed when switching to the Table display mode.
LD Modules: Evaluation of Optical Transceiver, etc., Characteristics
Combining the MS9740B with Anritsu’s MP2110A (all-in-one instrument incorporating bit error rate tester and sampling oscilloscope) supports simultaneous BER, Eye Pattern, and optical spectrum measurements at evaluation of optical transceivers, such as SFP and QSFP28 modules.
At optical-transceiver spectrum measurement, all key test items required for evaluating active optical devices (center wavelength, optical level, OSNR, etc.) are displayed as a group on one screen for at-a-glance understanding of results.
WDM Filters: Analysis of Optical Bandpass Filters
Optical bandpass filter characteristics can be evaluated efficiently by measuring signal level, peak signal number, signal wavelengths, spacing (wavelength), passband, and ripple, using the WDM Filter analysis function.
