CPAK vs QSFP28: Understanding the Key Differences

Introduction

In fiber optic systems, CPAK and QSFP28 are two distinct transceiver form factors designed for high-speed 100 Gigabit Ethernet (100GbE) connectivity. While both serve similar functions, they differ in design, compatibility, and application. This page compares CPAK vs QSFP28 and mentions the difference between CPAK and QSFP28.

CPAK (Cisco Packet Optical Advanced Kit)

It is a proprietary transceiver form factor developed by Cisco to deliver 100 GbE connectivity. CPAK has been designed specifically for Cisco networking equipment, such as ASR and Nexus series routers and switches. The CPAK modules are developed to address high density, low power requirements of data centers and service provider networks.

Figure 1 depicts the CPAK transceiver. They are smaller than CFP2 modules and consume less power than CFP2. It utilizes CMOS photonics technology which provides higher performance and scalability. They are available in various models to support different distances and fiber types, including single mode and multi mode fibers.

QSFP28 (Quad Small Form-Factor Pluggable 28)

QSFP28 is compact and hot pluggable transceiver. It is designed for 100GbE applications. It supports 4 transmit (Tx) and 4 receiver (Rx) channels. Each channel supports 25 Gbps with total of about 100 Gbps.

Figure 2 depicts the dimension of QSFP28. It’s compact size allows more ports per switch or router which maximizes bandwidth in limited spaces. Being standardized, QSFP28 modules are compatible across different equipments from multiple vendors.

• The common QSFP28 variants include SR4, LR4, CWDM4, PSM4 and ZR4.

Comparison between CPAK and QSFP28

Summary

CPAK transceivers are tailored for Cisco environments, offering compact size and energy efficiency. QSFP28 transceivers provide standardized solutions suitable for diverse networking scenarios across multiple vendors.