Keithley 2502 Fiber Alignment Photodiode Meter

The Keithley 2502 Fiber Alignment Photodiode Meter is a dual-channel instrument engineered for precision optical power measurements and fiber-to-photodiode alignment optimization. It minimizes insertion loss and maximizes signal strength in fiber optic systems through accurate current and voltage characterization. The 2502 serves research, development, and manufacturing environments requiring critical fiber alignment for product performance and quality control.

Technical Specifications

Measurement Ranges & Resolution

• Current measurement: 1 fA to 20 mA, 1 fA resolution


• Voltage bias source: ±10 V or ±100 V selectable


• Dark current measurement: 2 nA range optimized at 1 fA resolution with REL function for offset subtraction


• Maximum voltage source/measure: 100 V


• Analog output: 0–10 V for optical power feedback Electrical Performance


• Measurement speed: 900 readings per second per channel at 4½-digit resolution


• Input bias current: 50 fA max @ 23°C


• Input voltage burden: 4.0 mV max


• Voltage source slew rate: 3.0 ms/V typical


• Common mode voltage: 200 VDC


• Common mode isolation: 10⁹ Ω typical in parallel with 150 nF


• Source capacitance: 10.0 nF typical Data & Control


• Buffer memory: 3000-point per channel (6000 total) with timestamp logging


• Digital I/O: 1 trigger input, 4 TTL/relay drive outputs (33 V @ 500 mA, diode clamped)


• Serial interfaces: IEEE-488 and RS-232


• Trigger Link hardware handshaking Physical & Environmental


• Dimensions: 89 mm H × 213 mm W × 370 mm D


• Weight: 6.8 kg


• Power supply: 100/120/220/240 V ±10%, selectable; 50/60 Hz


• Power dissipation: 60 VA


• Vibration: MIL-T-28800F


• Warm-up time: 1 hour to rated accuracy

Key Features

• Dual-channel simultaneous measurement with independent bias control


• Selectable ±10 V (large-area photodiodes) and ±100 V (avalanche photodiodes) bias ranges


• LIV testing capability for laser diode modules integrating alignment and characterization


• Optical power measurement when paired with Model 2500INT Integrating Sphere


• High-speed data acquisition up to 900 readings/second per channel

Typical Applications

• Fiber-to-photodiode alignment and optimization


• Photodiode dark current and responsivity characterization


• Laser diode module LIV testing


• Optical power measurement in fiber optic component development


• Quality control and performance validation in manufacturing

Compatibility & Integration The 2502 interfaces via IEEE-488 and RS-232 for system integration. TTL/relay outputs and trigger inputs enable synchronization with external test equipment and automation systems. Integration with the Model 2500INT Integrating Sphere extends measurement capability to direct optical power assessment.