Used Optical Attenuators for Sale — Fixed & Variable VOA

A fixed optical attenuator inserts a precise, unchanging amount of loss — typically 1, 3, 5, 10, or 20 dB — into a fiber link. It is used to bring a signal within the dynamic range of a receiver or power meter. A variable optical attenuator (VOA) lets you adjust the attenuation continuously across a range, typically 0 to 60 dB or more. VOAs are used in test setups where you need to sweep the signal level, in receiver sensitivity testing, and in optical switch and ROADM characterization where the attenuation needs to change programmatically.

Most benchtop VOAs use FC/PC or FC/APC connectors on the input and output. Keysight and Agilent 815xx series use proprietary push-pull FC-style connectors compatible with their lightwave system platform. Inline fixed attenuators are available with FC, SC, LC, and ST connectors in both PC and APC polish. When buying used, confirm the connector type and polish before ordering — an FC/PC attenuator on an APC system introduces significant back-reflection.

NIST-traceable calibration for an optical attenuator at Aumictech covers attenuation accuracy at 5 or more set values across the full range, attenuation linearity, wavelength-dependent attenuation at 1310 nm, 1490 nm, and 1550 nm, insertion loss at the 0 dB position, and PDL on request. Standard calibration is $450 with a pass/fail certificate. Calibration with full measured data is $650. Turnaround 1 to 3 business days.

PDL is the difference in insertion loss between the polarization state that experiences maximum loss and the one that experiences minimum loss. On a VOA in a test setup, PDL in the attenuator adds polarization-dependent measurement error to every level-dependent measurement — receiver sensitivity, gain tilt, power calibration. High-quality benchtop VOAs like the Agilent 81570A specify PDL under 0.05 dB. On a VOA with 0.3 dB PDL, your level uncertainty is at least 0.3 dB regardless of how well calibrated the power meter is.

The Agilent 81570A and 81571A offer up to 60 dB of attenuation range. The EXFO FVA-620 covers 0 to 65 dB. JDS HA9 series attenuators cover up to 60 dB. Dynamic range beyond 60 dB typically requires two attenuators in series — Agilent offers a dual-stage configuration for this. In practice, measurement uncertainty increases at high attenuation settings, and the usable dynamic range is limited by the noise floor of the power meter receiving the attenuated signal.

The most common failure on motor-driven VOAs is wear in the attenuation mechanism — the attenuator becomes non-monotonic, develops steps, or loses smooth control. On the Agilent 81570A and 81571A, gear wear in the neutral density filter drive mechanism is the most frequently seen issue. Optical port contamination is the second most common problem, causing excess insertion loss that appears as attenuator failure. Cleaning the ports with proper fiber optic cleaning tools resolves many apparent faults before any mechanical repair is needed.

A benchtop VOA is a standalone instrument with its own power supply, display, and GPIB or USB control interface. It is the right choice for characterization work where you need programmable level control in a test setup. An inline VOA module (such as Agilent 81570A in an 8163B or 8164B mainframe) eliminates a separate power supply and allows the attenuator to be triggered and synchronized with the mainframe sweep. The module format is preferred in production and swept-wavelength measurement setups. Both calibrate the same way.

Most benchtop VOAs are designed and calibrated for singlemode fiber operation at telecom wavelengths (1250 to 1650 nm). Using them with multimode fiber changes the coupling efficiency and makes the attenuator reading unreliable — you will not get the labeled attenuation. For multimode work at 850 nm or 1300 nm, use an attenuator specified for multimode operation with the appropriate connector and wavelength range.