8504B Agilent Keysight HP Fiber Optic Equipment

The 8504B is a fiber optic equipment from Agilent Keysight HP.


  • The Keysight 8504B precision reflectometer provides state-of-the-art lightwave reflection measurements. Individual reflections are measured and displayed as a function of distance or position. Return loss measurements beyond 80 dB are achievable, even when larger reflections are present in the measurement path. Two reflections can be closer than 25 µm (equivalent distance in air) and still be individually identified.


  • The 8504B precision reflectometer serves as a powerful tool in the development and testing of systems and components. Accurate characterization of reflections is extremely important for a variety of high-performance lightwave systems and components. The relative intensity noise (RIN) and modulation bandwidth of DFB and other narrow linewidth lasers can be greatly affected by even very small amounts of backreflected light. Reflected signals can also cause distortion or bit errors in highspeed communications systems. An isolator, often used to reduce the reflections seen by a DFB laser, can itself be a source of reflections. This isolator is a complex structure. Each of the elements’ contribution to the total return loss can be easily determined.


Return Loss Range-

  • 1300 nm    10 to 80 dB
  • 1550 nm1    10 to 80 dB

Return Loss Accuracy-

  • ±2.0 dB 

Two-Event Spatial Resolution-

  • 1300 nm   25 (17) um
  • 1550 nm   65 (44) um

Two-Event Spatial Accuracy-

  • 1 to 10 mm    ±2 % of span
  • 10 to 400 mm    ±1 % of span 

Spurious Response-                                    Relative Distance from Largest Reflection

(dB below the largest reflection): –20 to –10 mm     –10 to 0 mm     0 to +10 mm     +10 to +20 mm

1300 nm                                    –55 dB                 –45 dB             –65 dB               –65 dB

1550 nm                                    –62 dB                 –62 dB             –62 dB               –62 dB 

The Agilent 8504B provides high levels of measurement capability, allowing you to see reflections that were difficult if not impossible to measure before. With over 80 dB of measurement dynamic range, the 8504B is a valuable tool wherever very sensitive measurements of return loss are required. The 8504B precision reflectometer is used to measure return loss on a variety of connectorized components in single-mode fiber. For instance, not only can the 8504B measure standard fiber-optic connectors, it also can measure backreflections from today’s state-of-the-art connectors. Using simple reflectometry techniques, precision return loss measurements are achieved without requiring elaborate connections to the instrument.

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