# 400 GbE Technology Demonstration Using CFP8 Pluggable Modules
## 1 Introduction  
Processing information and transmitting information are two fundamental functions in communication networks [1]. From a quantum physics perspective, particles can be classified as fermions or bosons. Electrons follow Fermi-Dirac statistics, while Bose-Einstein statistics apply to photons. Due to strong interaction, electrons are ideal for processing information. As there is minimal interaction between bosons, photons are ideal for transmitting information in different degrees of freedom including wavelength, time, amplitude, phase, polarization, mode, and space [2; 3]. Figure 1 illustrates the architecture of a core router, which is widely used in today's communication networks. A typical router includes a routing engine (RE), routing control board (RCB), physical interface card (PIC), flexible PIC concentrator (FPC), and switch interface board (SIB). Information processing in the communication network is mainly performed by these functional units, which is in the electron domain. Moreover, some of Juniper's packet optics products on the PTX platform are also shown in Figure 1. Information transmission is mainly performed by these functional units, which is in the photon domain. The integrated photonics line card (IPLC) tightlycouples a \(1\times 2\) wavelength selective switching (WSS), embedded bi-directional switch gain amplifiers, optical multiplexer/de-multiplexers, and optical supervisory channel for optical management into a single package that supports up to 64 ITU-T C-band wavelengths at 50 GHz spacing via an IPLC expansion line card. P3-15-U-QSFP28 and P2-PTX-5-100G-WDM are PTX Series PICs that support 15 QSFP28 and 5 CFP2 modules. In 2017, standardization of the 400 Gigabit Ethernet (400 GE) was ratified by the IEEE P802.3 bs Task Force [4]. This paves the way for deployment of 400 GE in the network. It is expected that the demand for 400 GE will grow rapidly over the next couple of years [5]. Recently, multiple industrial line-side and client-side interoperability trials have been successfully demonstrated using 400 GE CFP8 pluggable optical modules [6; 7; 8]. These trials demonstrate that the ecosystem for the 400 GE application is mature. In this paper, we present a successful demonstration of the 400 GE physical interface card (PIC) integrated in the core internet protocol/multi-protocol label switching (IP/MPLS) router, with the CFP8-LR8 modules acting as the optical front end. IEEE defines the optical and electrical parameters for the physical media dependent (PMD) to guarantee interoperability between PMDs. The physical implementations of PMDs are defined by multi-source agreement (MSA) instead. Currently, there are still multiple MSAs defining pluggable optical modules. Figure 2 below shows the comparison between different form factors defined by multiple MSAs [9; 10; 11; 12; 13; 14; 15; 16]. The most notable form factors for 400 GE defined by MSAs are QSFP-DD, OSFP and CFP8. Currently the industry is converging behind QSFP-DD due to the high port density on the front panel, backward compatibility with QSFP28/QSFP+, and large ecosystem. Figure 1: Typical architecture of core router and Juniper packet optical product. RE: routing engine; RCB: routing control board; PIC: physical interface card; FPC: Flexible PIC concentrator; SIB: switch interface board. Figure 2: Form factors and electrical lanes for pluggable optical modules. On-off-keying (OOK) has been the modulation format for 40 Gigabit Ethernet (40 GE) and 100 Gigabit Ethernet (100 GE). The IEEE 802.3 bs has selected 4-level pulse amplitude modulation (PAM4) for 400 GE transmission. Compared with OOK, the required baud rate of PAM4 could be reduced by a factor of two when keeping the desired net data rate constant. Thus, the transceiver implements PAM4 with fewer optical lanes/lower bandwidth components. This leads to lower cost, smaller power consumption and a denser footprint.