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QSFP28 ZR4 Module White Paper

1      Overview

HiSilicon’s QSFP28 ZR4 is for 100 Gbps Ethernet applications. It is intended for use between data centers between switches, routers, trasmission equipment etc, and the optical distance is up to 80km over a SingleMode (SM) fiber.

The transceiver integrates the receiver and transmit path on one module. On the transmit side, four lanes of serial data (NRZ) are recovered by a CDR and passed to four laser drivers, which control four lasers with center wavelengths of 1296 nm,1300nm,1305nm and 1309nm. The optical signals are multiplexed to a single mode fiber through an standard LC connector. On the receiver side ,four lanes of optical data streams are amplified by an SOA, then the optical signal are de-multiplexed by an integrated optical demultiplexer. Each data stream is recovered by a PIN detector, then through the transimpedance amplifier and CDR pass to a CAUI-4 compliant output driver. A block diagram is shown in Figure 1.

Figure 1: QSFP28 ZR4 Diagram

2      Application Notes

Metro and DCI, referring to hypercale data centers and large inernet exchanges connected inside the city and who requie many high bandwidth connections at 100G+ data rates. The focus on simplified operation, less space, low cost, and low power consumption.

Traditionally, switch vendors using CFP/CFP2 transceiver types with their equipment for DCI.

However, the dedicated line card is necessary because of the big power consumption, large size of CFP/CFP2 modules. Recent developments in direct detect 100G transceivers, for example, XXX QSFP28 PAM4 DWDM transceiver, provide another option. The main disadvantage is that PAM4 requires amplification and dispersion compensation system on the optical link for reach longer than 5km at 100Gbits, which induce that the end-to-end cost is higher. The DCI operator needs to deploy the Mux/Demux, EDFA, and DCM, which may do not exist in the current network. Keep in mind that XXX solution does not compatiable with 50GHz Mux/Demux.

Figure 2: XXX Solution

However, QSFP28 ZR4 overcome the drawbacks of CFP/CFP2 for their large form factor and high power consumption; at the same time, it can reach up to 80km and deployed based on dark fiber, without considering DWDM components, which is a true plug-and-play solution. s shown in Figure 3 below:

Figure 3: QSFP28 ZR4 Solution.

The following table clearly shows that the power budget of XXX module is only around 10dB, and dispersion compensation MUST be considered for the network design. Futhermore, QSFP28 ZR4 is better for the case tempterature also.

Parameters

QSFP28 ZR4

XXX

TOSA

4*EML

2* Silicon Photonics

Wavelengths

LWDM

1296 nm,1300nm,1305nm 1309nm

100G DMDM over 2

wavelengths on a 50Ghz grid

Modulation Format

NRZ

PAM4

Transmission Distance

80km

80km

Case temperature

0~70℃

20~70℃

Power Consumption

6.5W

5W

Dispersion tolerance

N/A (*note1)

±100ps/nm

Tx Power in AOP

2dBm

-11~-8dBm

Rx Sensitivity in AOP

-28dBm

-2~6dBm

Power budget

30dB

10dBm

*note1: work in the zero dispersion windows of 1310nm wavelength

Another alternative solution is based on coherent technology, which is usually used for long hual and metro transmission. The Coherent technology has adopted more advances modulations such as QPSK, 8QAM or 16QAM enabling to double, triple or quadruple the bitrates. However, this modulation requires an advanced technology which is coherent detection on receiver side and a DSP to correct the dispersion. While the cost per bit remains interesting, the components costs are high, and the pluggable modules require space and enough power, only available on CFP and CFP2 pluggable form factors. Of course, coherent modules can also be inserted into switch/router board for IPoDWDM scenario. Compared to XXX module it can eliminate DCM and OA components if the distance is lower than 80km and fiber quality is good.

Parameters

Coherent Module (CFP/CFP2)

Host FEC

KP4(not support KR4)

Wavelengths

1 wavelength, DWDM grid

Modulation Format

NRZ DP-QPSK

Transmission Distance

80Km

Case temperature

0~70℃

Power Dissipation

15W

Dispersion tolerance

2400ps/nm

Tx Power

-6dBm

Rx Sensitivity

-30dBm

Power budget

24dB

3      Summary

100GE QSFP28 ZR4 module can support 80km based on SM fiber, low cost, low power consumption, compact, plug and play, which is dedicated for metro and DCI scenario.


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