400G ZR QSFP-DD DCO modules are based on DP- 16QAM supporting extended C-band, polarization diversity coherent detection and advanced electronic link equalization. Chromatic dispersion compensation can be applied to the receive side of the demodulator. This module is managed utilizing the Two Wire Interface that is specified in the Common Management Interface Specification (CMIS).

The module uses a 76-pin QSFP-DD MSA QSFP-DD Hardware Specification connector for all electrical interfaces with the host card, whereas the optical interfaces on the line side are provided through the optical receptacles on the QSFP-DD. The module can be portioned into three functional parts: TX path, RX path and Control & Power block.

The host interface is comprised of a total of 8 high-speed SerDes lanes. This allows module to support one interfaces for 400G application: an independent double 4-Lane mode client interfaces (for 400GbE application) and four independent double lane mode client interfaces (for 4*100GbE application).

The management communication interface provides a number of elementary management operations that allow the host to read from or write to byte-sized management registers in the management memory map of the module. There are read and write operations both for single bytes and for contiguous byte sequences. Two types of read operations, either with implicit addressing (read from current address) or with explicit addressing, are supported.

The management communication interface distinguishes a role and a s role. The host shall be the and the module shall be the s.

The initiates all operations that lead to data transfer. Data can be transferred from the to the s (in write operations) and from the s to the (in read operations).

Features

● Support Flex-grid channel spacing DWDM in C-band

● Support Client-side Interfaces: 400GAUI-8/4*100GAUI-2

● Support Line-side DP-16QAM with CFEC

● Standard QSFP-DD type 2 form factor

● 76pin QSFP-DD MSA compliant connector

● Compliant to CMIS 5.0

● Compliant to OIF Implementation Agreement for Coherent CMIS, Rev 01.1

● OIF-400ZR-01.0_reduced2.pdf

● RoHS compliant

Typical Application

The application field of the module is widely used from short haul (ZR) to Metro(MR) interconnects. As shown  in figure1, it is comprised of high-data lanes, a single 3.3V power supply, an IIC interface for module control and status report, and dedicated alarm and control pins (not shown on the figure1).

 Figure 1. Transceiver Block Diagram

Host Interface

The module support for wide applications with Host interfaces: 400GAUI-8/100GUI-2. The Host interface conform to existing protocol standards and operate over standard physical layer specifications. The termination, mapping and/or aggregation of this signal is into an internal ZR frame structure. The ZR frame structure is then adapted to the CFEC engine and DSP framed for transmission over the coherent media Interface. The Host interface signaling conform to existing protocol and electrical standards as defined by IEEE 802.3TM-2018.

The Host Interface compliant to very short reach high speed chip-to-module electrical interface CEI-56G- VSR-PAM4 for PAM4 coding.

Media Interface

The media interface utilizes DP-16QAM modulation, polarization diversity coherent detection, and advanced electronic link equalization with omatic dispersion and differential group delay compensation.

The module terminates the host interface signal then maps and aggregates them into an internal ZR frame structure. The ZR frame structure is then adapted to the CFEC engine and DSP framed for transmission over the coherent media interface.

Host Electrical Connector & Pin Assignments

The electrical interfaces, including pad assignments for data, control, status and power supplies and host PCB layout requirements, of the module is fully compliant with the QSFP-DD MSA QSFP-DD-Hardware Specification, Rev 5.0.

The case of the QSFP-DD module is isolated from the module’s circuit ground, GND, to provide the equipment designer flexibility regarding connections between external electromagnetic interference shields and circuit ground, GND, of the module.

  Figure 2. MSA Compliant Connector 

Absolute Maximum Ratings

It has to be noted that the operation in excess of any individual absolute maximum ratings might cause permanent damage to this module.

Operating Conditions

Power Supply

The 400G ZR QSFP-DD DCO is a Power Class 8 module. In order to avoid exceeding the host system power capacity, upon hot-plug, power cycle or reset, all QSFP-DD modules shall power up in Low Power  Mode if LPMode is asserted. If LPMode is not asserted the module will proceed to High Power Mode without host intervention. Specification values for maximum instantaneous, sustained and steady state currents at each power class are given in table 5. The power supply requirements are specified in the table below.

Hardware Control and Status Pins

In addition to the 2-wire serial interface the module has the following low speed signals for control and status:

● ModSelL

● ResetL

● LPMode

● ModPrsL

● IntL

● Epps

ModSelL

The ModSelL is an input signal that shall be pulled to Vcc in the QSFP-DD module. When held low by the host, the module responds to 2-wire serial communication commands. The ModSelL allows the use of multiple QSFP-DD modules on a single 2-wire interface bus. When ModSelL is “High”, the module shall not respond to or acknowledge any 2-wire interface communication from the host.

In order to avoid conflicts, the host system shall not attempt 2-wire interface communications within the ModSelL de-assert time after any QSFP-DD modules are deed. Similarly, the host must wait at least for the period of the ModSelL assert time before communicating with the newly ed module. The assertion and de- asserting periods of different modules may overlap as long as the above timing requirements are met.

ResetL

The ResetL signal shall be pulled to Vcc in the module. A low level on the ResetL signal for longer than the minimum pulse length (t_Reset_init) initiates a complete module reset, returning all user module settings to their default state.

LPMode

LPMode is an input signal. The LPMode signal shall be pulled up to Vcc in the QSFP-DD module. LPMode is used in the control of the module power mode.

See CMIS Section 6.3.1.3.

ModPrsL

ModPrsL shall be pulled up to Vcc Host on the host board and pulled low in the module. The ModPrsL is asserted “Low” when the module is ed. The ModPrsL is deasserted “High” when the module is physically absent from the host connector due to the pull-up resistor on the host board.

Low speed signaling other than the SCL and SDA interface is based on Low Voltage TTL (LVTTL) operating at Vcc. Vcc refers to the generic supply voltages of VccTx, VccRx, Vcc host or Vcc1. Hosts shall use a pull-up resistor connected to Vcc host on each of the 2-wire interface SCL (clock), SDA (data), and all low speed status outputs. The SCL and SDA is a hot plug interface that may support a bus topology. During module ion or removal, the module may implement a pre-ge circuit which prevents corrupting data transfers from other modules that are already using the bus.

The QSFP-DD low speed electrical specifications are given in table 6. This specification ensures compatibility between host bus s and the 2-wire interface.

Physical Layer

The physical layer supporting communication between host and module is the Two Wire serial Interface (TWI). The TWI consists of a clock signal (SCL) and a data signal (SDA).

SCL and SDA comprise a 2-wire serial interface between the host and module using the TWI protocol. SCL is defined as the serial interface clock signal and SDA as the serial interface data signal. Both signals are open-drain and require pull-up resistors to +3.3V on the host. The pull-up resistor value shall be 1k ohms to 4.7k ohms depending on capacitive load.

Both signals (SCL and SDA) are bidirectional open-collector pins and require an external pull-up to VCC on   the host PCB. Activating the line requires pulling it down (wired ). The total capacitance on the bus should not exceed 400pF.

This 2-wire interface supports bus speeds:

· Fast mode - I2C Fast-mode (Fm) ≤ 400 kbit/s

· Fast mode plus - I2C Fast-mode Plus (Fm+) ≤ 1 Mbit/s

The SDA signal is bi-directional. During binary data transfer, the SDA signal shall transition when SCL is low.SDA transitions when SCL is high are used to mark either the beginning (START) or ending (STOP) of a data transfer.

High Speed Electrical Specifications

The transmitter and receiver comply with the CEI-56G-VSR-PAM4 electrical specification (OIF-CEI-04.0).

The data lines are AC-coupled and terminated in the module per the following figure from the QSFP-DD MSA. The high-speed signals follow the electrical specifications of CEI-56G-VSR-PAM as defined in OIF-CEI-04.0.

The high speed signals consist of 8 transmit and 8 receive differential pairs identified as TX[8:1]p / TX[8:1]n  and RX[8:1]p / RX[8:1]n. These signals can be operated in 400GAUI-8 depending on the capability of the host.400GAUI-8 mode provides 8 differential lanes using PAM4 signaling operating at 26.5625 GBaud. This results in 8 lanes of 50Gb/s for a total of 400Gb/s. This mode allows connection to PMD configurations of 400GUAI-8.

The following electrical acteristics are defined over the Recommended Operating Environment unless otherwise specified.

Electrical Characteristics for Transmitter

Electrical Characteristics for Receiver

Loopback

The module support loopback functionality. The host loopback (Loopback  ①) and the network loopback (Loopback  ②) are shown at bellowing figure 4. For details on controlling the loopback mode, please refer to   Reference [2]. In optional loopback, TXn is looped back to RXn, for example TX0+ to RX0+, on both host and media side.

  Figure3:Module Loopback Orientation

 Optical Specifications

All specifications given in this document are End-of-Life numbers and are valid under operating conditions unless specific noted:

Optical Transmitter Specifications

Optical Receiver Specifications

Insertion, Extraction and Retention Force

Applications

● DCI

● Metro Network