100G QSFP28 ZR4 Review

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100G QSFP28 ZR4 Review

Introduction

With the demand for higher bandwidths and greater distances increasing constantly in the telecommunications industry, spurring cloud traffic and subsequent data center and network growth, there is no doubt that there is a requirement for solutions that are both high-bandwidth and cost-effective. In this post we review our latest transceiver – 100G 80km QSFP28.

Current solutions for 80km

Available solutions for 100G 80km transmission are

  • Mux-ponder (10G DWDM + Mux/Demux +80km + EDFA)
  • O-E-O Repeaters (100G 40km + Repeater + 40km)
  • Coherent DWDM, CFP/CFP2
  • QSFP28 100G-DWDM PAM4 (EDFAs and DP compensation at ~ every 5km)

The above solutions are all very expensive and complex. 100G QSFP28 ZR4 aims to provide a simple straightforward solution for long distance 100G transmission.

100G ZR4 overview

The 100G ZR4 follows the QSFP28 form factor, the smallest for 100G 80km solutions, with the ability to transmit four 25G wavelengths: 1295.56nm, 1300.05nm, 1304.58nm, and 1310.19nm. It is fully compliant with the QSFP28 MSA industry standard and IEEE 802.3 100GBASE-ZR4 specifications. The transceiver also supports KR-4 FEC (Forward Error Correction) which both detect and correct errors, enhancing the quality and performance of the module.

  • Form factor : QSFP28
  • Data Format: 25.78125Gbps NRZ (CEI-28G-VSR)
  • Configuration: 4 lanes x 25G (electrical) => 4λ x 25G multiplexed into 1 fiber
  • Wavelengths: 1295.56nm 1300.05nm, 1304.58nm, 1309.14nm (LAN-WDM)
  • Power consumption: 4.5W (35C), = 5.5W (65C)
  • Support 60/65Km without FEC or 80km with KR-4 FEC for NRZ.

 

Why 1310nm?

The 100G QSFP28 ZR4 from Vitex incorporates a 1310nm laser. 1310nm wavelength has a few advantages over 1550nm in long distance data transmission. The attenuation is comparable for both, but dispersion penalty at 1550nm is very large. See chart below for comparison of 1310nm and 1550nm over standard single mode fiber.

If you do a simple link calculation using this Dispersion Penalty, the link length comes out to only about 40km.

Why SOA and not APD?

Our customers have asked us why the ZR4 module adopts an SOA and not an APD. After all, APD is widely deployed in 10G links for metro and access networks and they are more cost effective than the PIN+TIA approach.

However, APD has poor gain/bandwidth limitation and the dominant noise source is from the shot noise. Another advantage of SOAs is that they can amplify multiple WDM channels together in the optical domain.

Applications 

100G QSP28 ZR4 leverages the widely deployed 4x25Gbps NRZ optics without the need for optical amplification and dispersion compensation.

Large power budget = 30dB (2dBm – (- 28dBm) for short distance high loss links.

It offers the advantage of Point to point interconnect and routing applications between data centers and between data center and central offices without use of complicated, power hungry and expensive coherent solution or legacy CFP/CFP2.

If you have any questions on the QSFP28 100G ZR4, please don’t hesitate to contact us at info@vitextech.com.

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