Data Sheet
Broadcom AFBR-734SMZ-DS100
May 28, 2021
Description
The Broadcom
®
AFBR-734SMZ optical transceiver
supports high-speed serial links over multi-mode optical
fiber at 25.78 Gb/s (the serial line rate of 25GbE). The
product is compliant with Small Form Pluggable industry
agreements SFP and SFP28 for mechanical and low-speed
electrical specifications. High-speed electrical and optical
specifications are compliant with IEEE 802.3 for
25GBASE-SR.
The AFBR-734SMZ is a 850-nm transceiver that ensures
compliance with 25GBASE-SR specifications. Per the
requirements of 25GbE, internal clock and data recovery
(CDR) circuits are present on both electrical input and
electrical output of this transceiver. These CDRs lock at
25.78 Gb/s and cannot be bypassed.
Digital diagnostic monitoring information (DMI) is present in
the AFBR-734SMZ per the requirements of SFF-8472,
providing real time monitoring information of transceiver
laser, receiver, and environment conditions over an
SFF-8419 two-wire serial interface.
Related Products
AFBR-89CDDZ: 850-nm QSFP28 for 100GBASE-SR4
AFBR-79EQDZ: 850-nm QSFP+ for 40GBASE-SR4, 100m
AFBR-79E3PZ: 850-nm QSFP+ for 40GBASE-SR4,
300m
AFBR-709ISMZ: 850-nm SFP+ for 10GBASE-SR/SW,
–40°C/85°C
AFBR-709SMZ: 850-nm SFP+ for 10GBASE-SR/SW,
0°C/70°C
AFCT-709SM: 1310nm SFP+ for 10GBASE-LR,
0°C/70°C
Features
Compliant to RoHS directives
850-nm Vertical Cavity Surface Emitting Laser (VCSEL)
Class 1 eye safe per IEC60825-1 and CDRH
Wide temperature range (0°C to 70°C)
LC duplex connector optical interface conforming to
ANSI TIA/EIA604-10 (FOCIS 10A)
Diagnostic features per SFF-8472 “Diagnostic
Monitoring Interface for Optical Transceivers”
Enhanced operational features including variable
electrical EQ/emphasis settings
Real-time monitoring of the following:
– Transmitter average optical power
– Received average optical power
– Laser bias current
– Temperature
– Supply voltage
SFP28 mechanical specifications per SFF-8432
SFP28 compliant low speed interface per SFF-8419
25GBASE-SR compliant optical link distances
Applications
Ethernet switches (director, stand-alone, blade)
Ethernet NIC cards and adapters
Port side connections
Inter-switch or inter-chassis aggregated links
AFBR-734SMZ
25GbE SFP28 for Multi-Mode Optical Fiber
Digital Diagnostic SFP, 850-nm, Low Voltage
(3.3V) 25GBASE-SR Ethernet Optical
Transceiver
AFBR-734SMZ Data Sheet
25GbE SFP28 for Multi-Mode Optical Fiber Digital Diagnostic SFP, 850-nm, Low Voltage
(3.3V) 25GBASE-SR Ethernet Optical Transceiver
Broadcom AFBR-734SMZ-DS100
2
Transmitter Section
The transmitter section includes a Transmitter Optical
Sub-Assembly (TOSA), laser driver circuit, CDR circuit, and
an electrical input stage with variable equalization controls.
The TOSA contains a 850-nm VCSEL light source with
integral light monitoring function and imaging optics to
assure efficient optical coupling to the LC connector
interface. The TOSA is driven by a laser driver IC, which
uses the differential output from an integral Tx CDR stage to
modulate and regulate VCSEL optical power. As mandated
by IEEE 802.3, the integral CDR cleans up any incoming
jitter accumulated from the host ASIC, PCB traces, and SFP
electrical connector. Between the SFP electrical connector
and Tx CDR is a variable, two-wire serial controlled,
equalization circuit to optimize SFP performance with
nonideal incoming electrical waveforms.
Receiver Section
The receiver section includes a Receiver Optical
Sub-Assembly (ROSA), pre-amplification and
post-amplification circuit, CDR circuit, and an electrical
output stage with variable emphasis controls. The ROSA,
containing a high-speed PIN detector, pre-amplifier, and
imaging optics, efficiently couples light from the LC
connector interface and performs an optical to electrical
conversion. The resulting differential electrical signal
passes through a post amplification circuit and into a CDR
circuit for cleaning up accumulated jitter.
Note the Tx and Rx CDR is engaged regardless of TX/RX
Rate Select Control Input levels (both hardware and
software).
Digital Diagnostics
The AFBR-734SMZ is compliant to the Diagnostic
Monitoring Interface (DMI) defined in document SFF- 8472.
These features allow the host to access, using two-wire
serial, real-time diagnostic monitors of transmit optical
power, received optical power, temperature, supply voltage,
and laser operating current.
Low-Speed Interfaces
Conventional low-speed interface I/Os are available as
defined in the SFF-8419 document to manage coarse and
fine functions of the optical transceiver. On the transmit side,
a Tx_DISABLE input is provided for the host to turn on and
off the outgoing optical signal. A transmitter fault indicator
output, Tx_FAULT, is available for the SFP to signal a host
of a transmitter operational problem. A received optical
power loss of signal indicator, RX_LOS, is available to
advise the host of a receiver operational problem, such as a
low optical input condition.
Figure 1: Transceiver Functional Diagram