The HP/Agilent 81657A is a dual-wavelength Fabry-Perot laser source delivering stable, back-reflection-insensitive output at 1310 nm and 1550 nm. Operating at up to +13 dBm per channel with ±0.03 dB power stability over 24 hours, it performs insertion loss, optical return loss, and polarization-dependent loss measurements across fiber optic communication systems. The source couples to standard single-mode 9/125 µm fiber and integrates with Agilent 8163/8164/8166 series mainframes via separate optical interface connectors. Internal digital modulation modes span 270 Hz to 10 kHz with programmable 0–6 dB attenuation in 0.1 dB steps.
## Technical Specifications
• **Wavelengths:** 1310 nm (±15 nm), 1550 nm (±15 nm)
• **Output Power:** +13 dBm per channel (≈20 mW); maximum permissible CW output 52 mW
• **Power Stability:** ±0.03 dB over 24 hours; ±0.005 dB over 15 minutes
• **Spectral Bandwidth (rms):** <5.5 nm at 1310 nm; <7.5 nm at 1550 nm
• **Fiber Interface:** Single-mode 9/125 µm; beam waist 9 µm; numerical aperture 0.1
• **Attenuation Range:** 0–6 dB in 0.1 dB increments
• **Modulation Modes:** Internal digital at 270 Hz, 330 Hz, 1 kHz, 2 kHz; free selection 200 kHz–10 kHz; 50% duty cycle
• **Laser Classification:** Class 1M (IEC 60825-1:2001); Class IIIb (21 CFR 1040.10); Class 3A (IEC 60825-1:1998)
## Key Features
• Back-reflection immune operation ensures measurement stability without external isolation
• Dual-channel architecture eliminates need for multiple sources in 1310/1550 nm test suites
• Internal coherence control enables linewidth broadening for PDL characterization
• Programmable pulse modulation with shaped outputs
• Fault-triggered optical shutoff via internal safety circuitry
## Typical Applications
• Component insertion loss and return loss measurement
• Polarization-dependent loss (PDL) characterization
• Optical system-level performance validation
• Wavelength-dependent attenuation testing
## Compatibility & Integration
Designed for use with Agilent 8163A/B, 8164A/B, and 8166A/B mainframes. Requires Agilent 81000xI series optical interface connectors (sold separately). Integrates with optical power meter modules for complete test solutions.
