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Know Your 800GbE Transceiver

800 Gigabit Ethernet (800GbE or 800G) transceivers are optical modules capable of handling data rates of 800 Gbps. With a transmission rate of up to 800 Gbps, 800GbE transceivers offer double the capacity of their latest predecessor (400GbE transceivers). 800GbE transceivers are ideal for:

  • Any host platform with 800GbE ports

  • Networks with 800 gigabits data transmission

  • Telecommunication networks that require high-speed data transmission with minimal loss

An 800GbE transceiver uses multiple lanes of optical signals and advanced modulation techniques to achieve higher capacities. 800GbE transceivers employ multiplexing using multiple fibers. These transceivers also use a combination of fiber and wavelength multiplexing to transmit an optic signal. All 800 GbE client optics use 8 lanes of 100GbE with Pulse amplitude modulation 4-level (PAM4) modulation. PAM4 has a modulation of 53 Gbaud x 2 bits/symbol. 800GbE optics do not currently support Wavelength Division Multiplexing (WDM) systems that use only wavelength multiplexing and demultiplexing techniques.

800GbE transceivers support a range of Ethernet rates. The 800GbE transceivers can achieve their full 800 Gbps capacity through a single port. You can configure 800GbE transceivers to provide lower speeds of Ethernet with high-density. This configuration can include eight ports of 100GbE and 2 ports of 400GbE. 800GbE transceivers can handle multiple rates, which ensures that the transceivers are compatible with different transport requirements.

Juniper's 800GbE transceivers use the OSFP800 and QSFP-DD800 form factors. This document refers to the form factors as OSFP and QSFP-DD.

Modulation Methods

  • PAM4—PAM4 is a modulation method that combines two bits into a single symbol with four amplitude levels. That is, PAM4 effectively doubles the amount of data that you can transmit over a network.

    PAM4 has a high signal to noise ratio (SNR). As a result, the distance for data transmission must be shorter (up to a maximum of 10 km). It is necessary to configure forward error correction (FEC) to handle the loss of signal (LOS) integrity. You must configure FEC at both the transmitter and receiver ends of a communication link that uses 800GbE optical transceivers. When you configure FEC at both ends, the FEC algorithm encodes data before transmission and decodes and corrects the errors in data upon reception. In summary, PAM4 enables efficient short distance data transmission, but it demands more signal processing and error correction.

    Figure 1: PAM4 Modulation PAM4 Modulation

  • Non-return to zero (NRZ) modulation—Juniper's 800GbE optic clients do not support NRZ modulation.

Other technologies that 800GbE optics uses are:

  • Advanced digital signal processing (DSP) techniques and FEC algorithms—Enhances signal integrity and extend the reach of 800GbE transceivers over optical fiber.

  • Clock data recovery (CDR)—Extracts timing information from a data signal and ensures accurate data retrieval and transmission in an optic network.

See the Hardware Compatibility Tool for the list of transceivers, their specifications, and the list of devices supported by the transceivers.

Key Characteristics

The following are the key characteristics of an 800GbE transceiver:

  • Form factor—Common form factors for 800GbE transceivers include OSFP and QSFP-DD. The OSFP and QSFP-DD transceiver modules are designed to accommodate the higher power and thermal requirements of 800 Gbps of data transmission. The OSFP form factor has larger dimensions than the QSFP-DD form factor. It allows transceivers with OSFP form factor to handle higher power dissipation and provide better cooling solutions.

  • Fiber type and reach—The fiber type specifies the type of optical fiber (singlemode or multimode) compatible with 800GbE transceivers. The reach provides the maximum supported distance or range for an optical transceiver. It helps you to select the appropriate optical transceiver for different applications, such as inter-data center, intra-data center and so on.

  • Lane distribution—Juniper's 800GbE optics uses eight parallel lanes, either with multiple fiber pairs or wavelength multiplexing. 800GbE optics has parallel fibers that are used over shorter distances. Wavelength multiplexing using duplex single-mode fiber is used for longer distance optical communication. However, Juniper's 800GbE optics does not currently support it.

    Note:

    800GbE coherent DWDM optics (800ZR/ZR+) multiplexes the eight lanes using phase, amplitude, and polarization encoding onto a single optical wavelength. Juniper does not currently support coherent optics (ZR/ZR+) for 800 Gbps data transmission.

Juniper Optical Product Numbers

Juniper's optical components such as transceivers, cables, and connectors follow a naming convention. Each element in the product name corresponds to a specification. It helps you to better understand and select the appropriate optical component. For example:

  • QDD-2x400G-DR4

    • QDD—Short for QSFP-DD. It identifies the form-factor of the transceiver.

    • 2x400GbE—It indicates that the transceiver is capable of data transfer rates of 800 Gbps. The transceiver employs two 400GbE channels to achieve the 800GbE transmission rate.

    • DR4—Stands for 400GBase-DR4. It is a specific standard and indicates that each 400GbE channel uses four parallel lanes of 100 Gbps to deliver 400 Gbps.

Note:

You can distinguish the Juniper optical cables from transceivers using their product numbers. For example, QDD-800G-AOC-5M and OSFP-800G-AOC-10M are product names for Juniper cables. The product names specify the form factor (OSFP or QSFP-DD), the data transmission speed (800 Gbps, 400 Gbps, and so on), the cable type (AOC or DAC) and distance range (5 meter, 10 meter, and so on) for each cable.

800GbE (X8) Transceiver Architecture

The 8x100 gigabit architecture for an 800GbE transceiver uses eight lanes of 100 Gbps each. The following are the different components of an 800GbE transceiver architecture:

  • Host platforms—Juniper devices that support 800GbE architecture.

  • 8x100GbE electrical—The electrical interface between the switch and the transceiver components. It can transmit data over eight separate 100 Gbps electrical lanes.

  • PAM4 clock data recovery (CDR)/digital signal processor (DSP)—A PAM4 CDR/DSP supports each 100GbE lane. PAM4 effectively doubles the amount of data that you can transmit. The CDR is responsible for re-timing incoming data to reduce jitter. The DSP handles functions like equalization, error correction, and other signal processing tasks.

  • Driver x8—Drivers are electronic components that amplify the electrical signal. The x8 transceiver architecture has eight drivers. Each driver corresponds to a 100GbE lane.

  • Modulator x8—Eight modulators correspond to each of the 100GbE lanes (x8). 800GbE optics uses the following types of modulators:

    • Laser modulators—Laser modulators convert the amplified electrical signals into optical signals. 800GbE DR8 optics use laser modulators.

    • Vertical cavity surface emitting Lasers (VCSEL)—VCSEL is used for multimode optics such as SR8/VR8.

    • Directly modulated lasers (DMLs)—DMLs are used for single-mode optics such as DR8.

    • Externally modulated lasers (EMLs)—EMLs consist of a combination of modulators.

    • Continuous-wave (CW) fiber laser—A type of laser that emits a steady lightbeam. It is suitable for optics that require a higher loss budget.

  • 8x100GbE optical module—Optical interfaces that carry data in the form of light pulses. Each fiber in this model carries 100 Gbps of data.

  • Transimpedance amplifiers (TIA) x8—A TIA converts and amplifies the electrical current from the photodiode into an electrical voltage level. It can operate with very low signal levels that are typical for optical communication.

  • Photo-detector x8—It works in tandem with the TIA to convert the optical information back into electrical form.

An 8x100GbE architecture employs eight lanes to achieve a total data transmission rate of 800 Gbps. Each lane handles 100 Gbps.

Figure 2: 800GbE (X8) Transceiver Architecture 800GbE (X8) Transceiver Architecture

Optical PMD in 800GbE Transceiver Architecture

Optical physical medium dependent (PMD) sublayer is a component of an optic fiber's physical layer. It is responsible for the physical transmission of data. PMD formats the data correctly, then transmits and receives it through the optical medium. The following are some of the optical PMD models:

Optical PMD for 1λ solutions

  • 1λ single-mode fiber (SMF) solution for 800GbE DR8 and 800GbE DR8-2—It is designed for a single wavelength (1λ), SMF solution. 1λ SMF indicates the use of a single wavelength for light propagation. That is, only one mode or one path in the optical fiber allows light propagation. 1λ SMF benefits data transmission by minimizing loss. Also, it enables transmission over longer distances with less signal loss than multimode fibers. The 800GbE DR8 or DR8-2 transceivers utilize eight-channel, direct-reach modules that are preferred in coherent optics. See Figure 3.

  • 1λ multimode fiber (MMF) solution for 800GbE SR8—It is designed for a single-wavelength (1λ) operation in multimode, parallel fiber solutions with MPO, SN-MT, MMC or 8xSN/MDC connectors. 1λ refers to the use of a single wavelength. That is, the architecture can handle only one wavelength for the propagation of light. The use of single wavelength allows data transmission with minimal loss. The SR8 transceiver employs eight channels in the Short Reach (SR) mode that offers high data rates over a shorter distance.

    Figure 3: 1λ SMF Solution: 800GbE DR8, SR8, and DR8-2 1λ SMF Solution: 800GbE DR8, SR8, and DR8-2

Optical PMD for 4λ Solutions

  • 4λ SMF solution for 2xFR4/2xFR4-500—It is designed for a quad-wavelength (4λ) operation in SMF solutions. 4λ represents the usage of four differentiated wavelengths signaling four distinctive paths for light propagation. Due to the availability of multiple wavelengths, it can transfer more volumes of data. Also, it can mitigate loss during transmission. The 2xFR4 and 2xFR4-500 transceivers employ four channels in Far Reach or Forward Reach (FR) mode. It uses the four-level Pulse Amplitude Modulation (PAM4) technology. The 2xFR4-500 is suitable for medium-reach transmissions of 500 meters or less.

    Figure 4: 4λ SMF Solution: 2xFR4/2xFR4-500 4λ SMF Solution: 2xFR4/2xFR4-500

  • 4λ SMF solution for FR4/FR4-500—It is designed for a quad-wavelength (4λ) operation in SMF solutions that employ duplex fiber connectors. 4λ represents the use of four varying wavelengths. Thereby, it indicates four distinct wavelengths for light propagation. Due to the multiplicity of wavelengths, it can handle larger volumes of data transmission with manageable loss. The FR4 and FR4-500 transceivers employ four channels in Far Reach or Forward Reach (FR) mode. It uses the four-level Pulse Amplitude Modulation (PAM4) technology. The FR4-500 is suitable for medium-reach transmissions of 500 meters or less. The PAM4 design enables the architecture to effectively convert eight-channel transmission into four-channel transmission.

    Figure 5: 4λ SMF Solution: FR4/FR4-500 4λ SMF Solution: FR4/FR4-500

Optical PMD for 8λ Solutions

8λ SMF solution for FR8/LR8—It is designed for an octa-wavelength (8λ) operation in SMF solutions with duplex fiber connectors. 8λ denotes the use of eight distinct wavelengths. That is, the architecture can simultaneously handle eight separate wavelengths of light. The use of multiple wavelengths improves data transmission. The FR8 and LR8 transceivers employ eight channels in the Far Reach or Forward Reach (FR) and Long Reach (LR) mode respectively. It adopts the four-level Pulse Amplitude Modulation (PAM4) technology. The architecture enables the system to divide the eight channels of transmission into two sets of four channels each or to retain the eight channels using PAM4 CDR.

Figure 6: 8λ SMF Solution: FR8/LR8 8λ SMF Solution: FR8/LR8