Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
ON THIS PAGE
 

Know Your 800G Transceiver

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

  • Any host platform with 800G ports

  • Networks with 800 Gbps data transmission

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

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

800G transceivers support multiple transmission rates and breakout modes to ensure compatibility with various network transport requirements. This flexibility allows a single physical transceiver to be logically divided into multiple lower-speed Ethernet ports, adapting to different deployment scenarios:

  • 1x800G—The transceiver functions as a single 800G port to achieve a total capacity of 800 Gbps.

  • 2x400G—The breakout cable provides the port as two separate 400G ports to achieve a total capacity of 800 Gbps.

  • 8x100G—The transceiver can break out into eight separate 100G ports to achieve a total capacity of 800 Gbps.

Juniper's 800G 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 higher than required signal to noise ratio (SNR) and is susceptible to four-Wave Mixing (FWM). FWM is a nonlinear optical phenomenon that occurs in fiber-optic communication systems when multiple optical signals (wavelengths) interact within the fiber. The challenge of achieving 800G optical transmission over distances greater than 10 km using PAM4 modulation is mainly due to FWM. It is necessary to configure forward error correction (FEC) to handle the signal integrity. You must configure FEC at both the transmitter and receiver ends of a communication link that uses 800G 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 Waveform diagram showing a PAM4 signal for binary sequence 0110100 and an eye diagram illustrating PAM4 signal quality with levels 11, 10, 01, and 00.

  • Non-return to zero (NRZ) modulation—Non-return to zero (NRZ) modulation is commonly used as the modulation format for lower speed client optics up to 100G. However, industry standards for 800G optics do not use NRZ modulation. Hence, Juniper's 800G clients optics do not support this.

800G optical transceivers use the following technologies:

Digital Signal Processing

Advanced digital signal processing (DSP) techniques enhance signal integrity and extend the reach of 800G transceivers over optical fiber.

Clock Data Recovery

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

Forward Error Correction

The 800G optical transceiver handles high transmission speeds. Hence, it is susceptible to errors caused by noise, signal distortions, and nonlinear effects. Forward Error Correction (FEC) is a method of error control in which the transmitter adds redundant data or parity bits to the original data stream. This redundancy allows the receiver to detect and correct errors without requiring retransmission. Retransmission is impractical in optical transceivers due to high latency and the need for real-time transmission.

FECs are implemented through FEC algorithms. FEC algorithms are specific mathematical techniques or coding schemes. FEC algorithms detect and correct errors in transmitted data without requiring retransmission. The FEC process involves two steps:

  • Encoding (at the Tx or transmitter)—The FEC algorithm processes the original data and adds redundant bits or parity bits based on a specific mathematical rule. The encoded data is then transmitted over the communication channel.

  • Decoding (at the Rx or Receiver)—The receiver uses the FEC algorithm to analyze the received data, including the redundant bits. If errors are detected, the algorithm attempts to correct them based on the redundancy.

The error correction capability of FEC depends on the specific algorithm used and the amount of redundancy added. Some of the commonly used FEC algorithms include:

  • Reed-Solomon (RS) FEC

  • Soft-Decision FEC (SD-FEC)

  • Low-Density Parity-Check (LDPC) Codes

  • Bose-Chaudhuri-Hocquenghem (BCH) Codes

  • Concatenated FEC

The choice of FEC algorithm depends on the specific requirements of the communication system:

  • Data Rate—High-speed systems require more efficient algorithms. This could be LDPC or turbo codes.
  • Error Characteristics—Burst errors are better handled by block codes such as Reed-Solomon.
  • Latency—Real-time applications such as video streaming require low-latency algorithms.
  • Power and Complexity—Systems with limited computational resources may use simpler codes like Hamming or BCH.

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

Second-Generation 800G Optics

The second generation of 800G optical transceivers from Juniper support eight pairs of electrical lanes with 100G per lane and four pairs of optical or media lanes with 200G per lane. These transceivers support the OSFP form factor across the following transceiver construction types:

  • Integrated heatsink (OSFP, air-cooled model)

  • Riding heatsink (ORHS, cold-plate liquid-cooled model)

The ORHS or riding heatsink variants are designed for ORv3 chassis that provide external liquid-cooling via the rack's heatsink mechanism. The OSFP or integrated heatsink variants are self-contained, air-cooled models with similar cooling mechanism as the first generation 800G optics.

The specifications and construction of the second generation of 800G optics make it compatible for deployment with 1600G optics. These optics are also backward compatible with the older standards, but with a reduced reach of 500 m instead of 2 km. Hence, a second-generation optical transceiver module can operate in two modes. For example, OSFP-800G-DR4-2 optical transceiver can operate either in the 800G-DR4-2 standard mode with 2 km reach or in 800G-DR4 standard mode with 500 m range.

The second-generation 800G optical transceivers have identical fiber type, maximum reach, and temperature range, making heatsink type and connector the key differentiators when selecting the optics. For more information on the second generation of 800G optical transceivers that Juniper currently supports, see Table 1.

Table 1: Second-Generation 800G Optics
Optical Transceiver Form Factor Heatsink Standard Fiber Type Maximum Reach Operating Temperature Connector Type
OSFP-800G-DR4-2 OSFP800 Integrated

800G-DR4-2

800G-DR4 (500 m)

 SMF 2 km

0 °C—70 °C

 MPO-12/APC
ORHS-800G-DR4-2 OSFP800-RHS Riding

800G-DR4-2

800G-DR4 (500 m)

 SMF 2 km

0 °C—70 °C

 MPO-12/APC
OSFP-800G-FR4 OSFP800 Integrated

800G-FR4

800G-FR4-500 (500 m)

 SMF 2 km

0 °C—70 °C

 LC/UPC
ORHS-800G-FR4 OSFP800-RHS Riding

800G-FR4

800G-FR4-500 (500 m)

 SMF 2 km

0 °C—70 °C

 LC/UPC

Modulation in Second-Generation 800G Optics

Second-generation 800G optics use PAM4 with four levels to achieve higher data rates on each optical lane. Unlike traditional non-return-to-zero (NRZ) signaling, which encodes 1 bit per symbol, PAM4 uses four distinct signal levels to encode 2 bits per symbol. This approach effectively doubles the amount of data transmitted per symbol while maintaining a practical signaling rate.

In a 4x200G transceiver architecture, PAM4 enables each optical lane to carry 200 Gbps of data, allowing four optical lanes to provide an aggregate bandwidth of 800 Gbps. By increasing the data rate per lane, PAM4 reduces the number of optical lanes required compared to earlier 800G implementations that relied on eight 100 Gbps optical lanes.

For more information on PAM4 modulation, see Modulation Methods.

Key Characteristics

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

  • Form factor—Common form factors for 800G 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 800G 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 800G optics uses eight parallel lanes, either with multiple fiber pairs or wavelength multiplexing. 800G optics has parallel fibers that are used over shorter distances. Wavelength multiplexing using duplex single-mode fiber is used for longer distance optical communication.

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.

    • 2x400G—It indicates that the transceiver supports break-out into two independent 400G Ethernet interfaces for data transmission.

    • DR4—Stands for 400GBase-DR4. It is a specific standard and indicates that each 400G 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.

800G (X8) Transceiver Architecture

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

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

  • 8x100G electrical—The electrical interface between the switch and the transceiver components. It can transmit data over eight separate 100 Gbps electrical lanes.

  • PAM4 CDR/DSP—It supports 100 Gbps electrical lanes. 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 100 Gbps electrical lane.

  • Modulator x8—Each of the eight laser modulators corresponds to one 100 Gbps electrical lane (x8). 800G optics uses the following types of 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. DMLs use distributed feedback (DFB) structures that incorporate a diffraction grating for stable direct modulation. Their modulation speed and transmission distance depend on the spectral line-width. A narrower line-width allows higher speeds and longer distances. In DMLs, data is modulated by adjusting the injection current on the laser diode, resulting in a compact design suitable for low-power applications.

    • Electro-absorption Modulated Laser (EMLs)—An EML integrates a laser diode with an electro-absorption modulator on a single chip. The laser operates continuously and the modulator turns the signal on and off.

    Unlike DMLs, EMLs maintain constant laser properties during modulation, offering advantages in higher speed and longer distance transmissions due to lower chromatic dispersion. EMLs are primarily used for speeds over 25 Gbps and distances of 10 kilometers to 40 kilometers in telecom applications.

  • 8x100G 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 8x100G architecture employs eight lanes to achieve a total data transmission rate of 800 Gbps. Each lane handles 100 Gbps.

Figure 2: 800G (X8) Transceiver Architecture Block diagram of 800G optical transceiver system: data flows from 800G switch through PAM4 CDR/DSP, Driver x8, Laser Modulator x8, Photo Detector x8, and TIA x8, handling 8x100G electrical inputs and outputs 8x100G optical signals.

Second-Generation 800G (4x200G) Transceiver Architecture

The 4x200 gigabit architecture for an 800G transceiver uses four optical lanes of 200 Gbps each while maintaining eight 100 Gbps electrical lanes toward the host platform. A gearbox DSP converts the eight 100 Gbps PAM4 electrical lanes into four 200 Gbps PAM4 optical lanes. The following are the different components of an 800G transceiver architecture:

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

  • 8x100G electrical—The electrical interface between the switch and the transceiver components. It transmits data over eight separate 100 Gbps electrical lanes.

  • Gearbox DSP (8x100G PAM4 to 4x200G PAM4)—The gearbox DSP aggregates eight 100 Gbps PAM4 electrical lanes into four 200 Gbps PAM4 optical lanes on the transmit path. On the receive path, it converts four 200 Gbps PAM4 optical lanes back into eight 100 Gbps PAM4 electrical lanes. This function enables interoperability between host systems using 100 Gbps electrical lanes and optical interfaces using 200 Gbps lanes.

  • PAM4 clock data recovery (CDR)/digital signal processor (DSP)—The PAM4 CDR/DSP supports the 200 Gbps PAM4 optical lanes. PAM4 effectively doubles the amount of data transmitted compared to traditional NRZ signaling. The CDR re-times incoming data to reduce jitter, while the DSP performs functions such as equalization, signal conditioning, error correction, and other signal processing operations.

  • Driver x4—Drivers are electronic components that amplify the electrical signal before transmission. The 4x200G transceiver architecture uses four drivers, with each driver corresponding to one 200 Gbps optical lane.

  • Laser Modulator x4—Four laser modulators correspond to the four 200 Gbps optical lanes. These optical transmitters convert the electrical PAM4 signals into optical signals for transmission over fiber. Depending on the optical type and transmission distance, the architecture can use technologies such as DMLs or EMLs.

  • 4x200G optical module—The optical interface carries data in the form of light pulses over four optical lanes. Each optical lane carries 200 Gbps of data, providing an aggregate bandwidth of 800 Gbps.

  • Transimpedance Amplifiers (TIA) x4—TIAs convert and amplify the electrical current received from the photodetectors into usable voltage signals. They are designed to operate with the very low signal levels typical in optical communication systems.

  • Photo-detector x4—The photodetectors convert incoming optical signals into electrical signals. They operate in conjunction with the TIAs to recover the transmitted data from the optical medium.

A 4x200G architecture employs four optical lanes to achieve a total data transmission rate of 800 Gbps. Each optical lane handles 200 Gbps, while the gearbox DSP performs lane conversion between the host-side 8x100G electrical interface and the network-side 4x200G optical interface.

Figure 3: Second-Generation 800G Transceiver Architecture Second-Generation 800G Transceiver Architecture