GAOTek QSFP28 SR4 Transceiver QXP28S-101, 100Gb/s and up to 2km

This 100Gbps, 850nm QSFP28 transceiver is used with a multimode fiber to reach up to 1.2 Miles (2km)




Key Features

  • Up to 27.952 Gbps Data rate per channel
  • Maximum link length of 328 Ft.(100m) links on OM3 multimode fiber
  • High-Reliability 850nm VCSEL technology
  • Electrically hot-pluggable
  • Digital diagnostic SFF-8436 compliant
  • Compliant with QSFP28 MSA
  • Power dissipation < 2.5 W
  • Case operating temperature range from 32°F to 158°F (0°C to 70°C)



Technical Specifications

Protocol2 Wire Serial Communication
Working RangeUp to 1.2 Miles (2km)
StandardsIEEE 802.3bm

SFF 8436


Data rate100 Gb/s
Wavelength850 nm
Transmitter Extinction Ratio2 dB
Receiver Sensitivity-10.3 dBm
Dimensions4.8 in x 0.72 in x0.33in(122×18.35×8.5 mm)
Supply Voltage-0.3 to 4V
Storage Temperature-40 °F to 185 °F (-40°C to 85°C)
Storage Ambient Humidity5% to 95%
Case Operating Temperature32°F to 158°F (0°C to 70°C)




  • Compliant to IEEE 802.3 bm
  • Compliant to SFF-8436
  • RoHS Compliant.

PIN Assignment:


  1. GND is the symbol for signal and supply (power) common for QSFP28 modules. All are common within the QSFP28 module and all module voltages are referenced to this potential unless otherwise noted. Connect these directly to the host board signal common ground plane.
  2. VccRx, Vcc1 and VccTx are the receiving and transmission power suppliers and shall be applied concurrently. Recommended host board power supply filtering is shown below. Vcc Rx, Vcc1 and Vcc Tx may be internally connected within the QSFP28 transceiver module in any combination. The connector pins are each rated for a maximum current of 500mA.

Optical Characteristics


Electrical Characteristics


  1. Connected directly to TX data input pins. AC coupled thereafter.
  2. Into 100 ohms differential termination.

Digital Diagnostic Functions

GAOTek GAO-QXP28S-101 support the 2-wire serial communication protocol as defined in the QSFP28 MSA which allows real-time access to the following operating parameters:

  • Transceiver temperature
  • Laser bias current
  • Transmitted optical power
  • Received optical power
  • Transceiver supply voltage

The operating and diagnostics information is monitored and reported by a Digital Diagnostics Transceiver Controller inside the transceiver, which is accessed through the 2-wire serial interface. When the serial protocol is activated, the serial clock signal (SCL pin) is generated by the host. The positive edge clocks data into the QSFP28 transceiver into those segments of its memory map that are not write-protected. The negative edge clocks data from the QSFP28 transceiver. The serial data signal (SDA pin) is bi-directional for serial data transfer. The host uses SDA in conjunction with SCL to mark the start and end of serial protocol activation. The memories are organized as a series of 8-bit data words that can be addressed individually or sequentially. The 2-wire serial interface provides sequential or random access to the 8 bit parameters, addressed from 00h to the maximum address of the memory.

This clause defines the Memory Map for QSFP28 transceiver used for serial ID, digital monitoring and certain control functions. The interface is mandatory for all QSFP28 devices. The memory map has been changed in order to accommodate 4 optical channels and limit the required memory space. The structure of the memory is shown in Figure QSFP28 Memory Map. The memory space is arranged into a lower, single page, address space of 128 bytes and multiple upper address space pages. This structure permits timely access to addresses in the lower page, e.g. Interrupt Flags and Monitors. Less time critical entries, e.g. serial ID information and threshold settings are available with the Page Select function. The structure also provides address expansion by adding additional upper pages as needed. For example, in Figure upper pages 01 and 02 are optional. Upper page 01 allows implementation of Application Select Table, and upper page 02 provides user read/write space. The lower page and upper pages 00 and 03 are always implemented. The interface address used is A0xh and is mainly used for time critical data like interrupt handling in order to enable a “one-time-read” for all data related to an interrupt situation. After an Interrupt, IntL, has been asserted, the host can read out the flag field to determine the effected channel and type of flag.

For more detailed information including memory map definitions, please see the QSFP28 MSA Specification.

Fig: QSFP28 Memory Map

Lower Memory Map

The lower 128 bytes of the 2-wire serial bus address space, see below Table, is used to access a variety of measurements and diagnostic functions, a set of control functions, and a means to select which of the various upper memory map pages are accessed on subsequent reads. This portion of the address space is always directly addressable and thus is chosen for monitoring and control functions that may need to be repeatedly accessed. The definition of identifier field is the same as page 00h Byte 128.

Table 1: Lower Memory Map


Status Indicator Bits

The Status Indicators are defined in the below table.

Interrupt Flags

A portion of the memory maps (Bytes 3 through 21), form a flag field. Within this field, the status of LOS and Tx Fault as well as alarms and warnings for the various monitored items is reported. For normal operation and default state, the bits in this field have the value of 0b. For the defined conditions of LOS, Tx Fault, module and channel alarms and warnings, the appropriate bit or bits are set, value = 1b. Once asserted, the bits remained set (latched) until cleared by a read operation that includes the affected bit or reset by the ResetL pin. The Channel Status Interrupt Flags are defined in below Table.

Table: Channel Status Interrupt Flags

The Module Monitor Interrupt Flags are defined in the below table.

The Channel Monitor Interrupt Flags are defined in the below Table.

Module Monitors

Real time monitoring for the QSFP28 module include transceiver temperature, transceiver supply voltage, and monitoring for each transmit and receive channel. Measured parameters are reported in 16-bit data fields, i.e., two concatenated bytes. These are shown in the below Table.

Table: Module Monitoring Values

Channel Monitoring

Real time channel monitoring is for each transmit and receive channel and includes optical input power , Tx bias current and Tx output Power. Measurements are calibrated over vendor specified operating temperature and voltage and should be interpreted as defined below. Alarm and warning threshold values should be interpreted in the same manner as real time 16-bit data. Table below defines the Channel Monitoring.

Table: Channel Monitoring Values

Control Bytes

Control Bytes are defined in below Table.

Host-Transceiver Interface Block Diagram

Outline Dimensions


  • Data center
  • Infiniband QDR
  • Fiber channel



Content missing