1. Product Positioning
The Keysight 81656A is a high-precision tunable laser source module specifically designed for optical communication testing, serving as a core component of Keysight's 81600B optical test platform. This module meets diverse testing requirements from R&D to mass production, with exceptional suitability for:
DWDM system validation
Optical device characterization
Coherent communication testing
Silicon photonics chip analysis
2. Core Performance Comparison Table
| Parameter Category | 81656A Standard | 81656A Advanced | Competitor Benchmark |
|---|
| Wavelength Range | 1480-1640nm | 1260-1650nm (Option) | 1520-1620nm |
| Wavelength Resolution | 0.1pm | 0.05pm | 1pm |
| Output Power | +13dBm ~ -90dBm | +15dBm ~ -100dBm | +10dBm ~ -80dBm |
| SMSR | >55dB | >60dB | >50dB |
| Linewidth | <100kHz | <50kHz | <200kHz |
| Power Stability | <0.01dB/24h | <0.005dB/24h | <0.03dB/24h |
| Modulation BW | DC-2GHz | DC-10GHz (Option) | DC-1GHz |
3. Key Subsystem Specifications
Laser Generation Unit
External Cavity Laser (ECL) design
Wavelength tuning: MEMS mirror + grating assembly
Temperature control accuracy: ±0.001℃
Power Control Module
Digital attenuator: 0.01dB step resolution
Power monitoring: Dual-detector redundancy
Dynamic range: 103dB (typical)
Modulator Performance
| Modulation Type | Specification |
|---|
| Amplitude Modulation | Extinction ratio >30dB |
| Frequency Modulation | ±2.5GHz tuning range |
| Phase Modulation | <0.1° phase noise |
4. System Integration Capabilities
Host Compatibility
Interface Performance Comparison
| Interface | Latency | Application Scenario |
|---|
| GPIB | 5ms | Legacy ATE systems |
| USB 3.0 | 2ms | Standalone control |
| LAN (LXI) | 1ms | Distributed test networks |
Automation Control
SCPI command set (300+ commands)
LabVIEW/Python driver libraries
Pre-installed Keysight N77xx test suite
5. Typical Test Configuration Example
DWDM Filter Test Setup:
Hardware Connection
81656A → Polarization controller → DUT → Power meter
↘ Wavelength meter (real-time calibration)
Software Configuration
laser.set_wavelength(1550.12) # Unit: nm
laser.set_power(0) # Unit: dBm
sweep(start=1540, stop=1560, step=0.01)
6. Maintenance & Calibration
Recommended Calibration Intervals
| Usage Environment | Interval |
|---|
| R&D lab (<8h/day) | 24 months |
| Production line (24/7) | 6 months |
| Field testing | Pre-mission |
Key Calibration Items
Wavelength accuracy (requires wavelength meter)
Power linearity calibration
Modulation response calibration
7. Product Selection Guide
Standard Version (81656A)
Advanced Version (81656A-020)
Ultra-Narrow Linewidth Option (81656A-NL)
8. Technological Evolution
Improvements vs. Previous Gen (81653A):
3× faster wavelength tuning (100nm/s → 300nm/s)
15dB wider power dynamic range
Added real-time wavelength locking
20% smaller module size
(Note: Actual performance may vary based on configuration and environment. For optimal performance, use with Keysight N7700A optical test software.)
Key Advantages Summary:
✔ Precision Tuning: 0.1pm wavelength resolution
✔ Ultra-Stable Output: <0.01dB power fluctuation
✔ Flexible Integration: Multi-module synchronization support
✔ Future-Ready: Compatible with 400G/800G test requirements
