Performance of 23-dBm PDFA for LWDM8 and CWDM4 wavelength range

Last updated on 04/23/2021

Introduction

In our previous post we did the first preview of our +23 dBm (200 mW) PDFA FL-AMP8612-OB prototype. The output from the PDFA exceeded +23 dBm with a sufficient margin. The measurement, however, was done only at one wavelength (1310 nm).

In this post we show more details of the amplifier characteristics – gain and noise figure at the 400GBASE-LR8 and CWDM4 wavelength ranges. These two wavelength ranges are of paramount importance for test and measurement of the next-gen Ethernet transceivers.

Amplification characteristics in the O-band

Test setup

Figure 1: Test setup.

The setup of the experiment is quite similar as the previous post. The only difference is that the measurement is controlled by a laptop PC for automated wavelength scanning in the O-band. The pump power was fixed to a level such that the output from the PDFA becomes +23 dBm, when the input is 0 dBm at 1310 nm. The measured gain spectrum and NF are shown in below.

Gain and NF of 23-dBm PDFA prototype

Figure 2: Gain and NF.

Applicability to LR8 and CWDM4 wavelengths

The two figures below show the gain curve, same as above, but now the LR8 and CWDM4 wavelength range (including wavelength tolerance) are marked. This shows that the amplifier may readily be used for transceiver testing, such as receiver stress testing or eye-pattern monitoring.

We have previously shown that the addition of a PDFA hardly add transmission penalty for 100GBASE-LR4 transmission in the booster amplifier configuration (see our previous post). As the configuration of this prototype is quite similar to that used in the previous post, we believe this prototype should hardly add transmission penalty, too.

17dB gain over LR8 range

Figure 3: 17dB gain over LR8 range.

10dB gain over CWDM4 range

Figure 4: 10dB gain over CWDM4 range.

Potential for further power scaling

All the results shown in the above were taken at 80% of full pump power. This is because some amount of operation margin is always needed as a commercial product. Here we show the gain spectrum measured at full pump power, just to demonstrate the potential of further power scaling.

Potential for further power scaling

Figure 5: Potential for further power scaling.

It is seen that the output power nearly reaches +27 dBm (500 mW) at 1290-1300 nm region. This result indicates, by using a more powerful pump source, a half-watt amplifier could be commercially feasible in the near future.

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