Linear InGaAs Optical Receiver Lab Buddy with Automatic Gain Control up to 56 Gbaud

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The DSC-R421 is a linear PIN + transimpedance amplifier that is primarily designed for 4-level Pulse Amplitude Modulation (PAM 4) and NRZ-ASK (PAM 2) modulation formats up to 56 Gbaud symbol rate in 1310 nm and 1550 nm single-mode systems. The R421 offers a variety of user-adjustable characteristics such as mode of operation (AGC or manual gain control), RF gain, output amplitude, and bandwidth.

The DSC-R421 is available in Discovery’s computer-controlled Lab Buddy instrument, where several critical parameters can be controlled and monitored using Standard Commands for Programmable Instruments (SCPI) compatible commands via standard RS232C-over-USB interface. The DC photocurrent is monitored over nanoampere to milliampere range and is continuously shown in Lab Buddy’s digital display.

DSCR-421 Linear PIN + Transimpedance Amplifier Lab Buddy

Fig1: DSC-R421 Lab Buddy instrument.

DSC-R421 - PAM4 NRZ Eye Diagram

Fig2: PAM4 & NRZ Eye Diagram.

Salient Features:

  • Two modes of operation: AGC or manual gain control
  • Differential Conversion gain up to 3000 V/W
  • High Responsivity at 1310 nm & 1550 nm
  • Maximum differential RF output > 500 mVpp
  • Low optical PDL (0.05 dB typical)


  • Ideal Test & Measurement Optical Front-End
  • Ethernet: 400GbE, 800GbE
  • Infiniband: EDR, HDR, NDR
  • Fiber Channel: 32GFC, 64GFC, 128GFC
  • RF-over-fiber link
DSCR-421 PAM4 Link Performance

Fig3: DSCR-421 PAM4 Link Performance.

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