HFBR-0536Z

HFBR-0536Z Datasheet

Many existing serial wire communication protocols were developed for differential line receivers or optocouplers that can sense the dc component of the data communication signal. This type of serial data is often called arbitrary duty factor data because it can remain in the logic “1” or logic “0” state for indefinite periods of time. Arbitrary duty factor data has an average value, which can instantaneously be anywhere between 0 percent and 100 percent of the binary signal’s amplitude, or in other words, arbitrary duty factor data contains dc components. Communication protocols that were developed specifically for use with copper wire often require an optical receiver that is dc coupled or capable of detecting if the data is changing from a high-to-low or low-to-high logic state. That is, the receiver needs to be an edge detector. At relatively modest data rates between zero and 10-Mbits/sec it is possible to construct dc coupled TTL-compatible fiberoptic receivers. The Avago Technologies HFBR-2521Z is a TTL-compatible, dc to 5-Mbit/sec receiver, and the HFBR-2528Z is a dc to 10-Mbit/sec CMOS or TTL-compatible receiver. Additional information about dc to 5-Mbit/ sec applications can be found in Avago Technologies AN-1035, and applications support for dc to 10-Mbit/sec applications can be obtained by reading AN-1080. This application note will focus on higher speed or higher performance arbitrary duty factor optical data communication links that work at higher data rates or greater distances than achievable with the HFBR-2521Z or HFBR- 2528Z components. The optical transceivers shown in this application note can also be used in burst-mode applications where the data is transmitted in packets and there are no transitions between bursts of date.

Part	Datasheet
HFBR-0536Z	HFBR-0536Z (pdf)

Related Parts	Information
HFBR-0536	HFBR-0536
HFBR-0537	HFBR-0537

PDF Datasheet Preview
Inexpensive dc to 32 MBd Fiberoptic Solutions for Industrial, Medical,Telecom, and Proprietary Data Communication Applications Application Note 1121 Introduction Low-cost fiberoptic data-communication links have been used to replace copper wire in numerous industrial, medical, and proprietary applications. The fiberoptic transmitter and receiver circuits in this publication address a wide range of applications. These recommended circuits are compatible with unencoded or burst-mode communication protocols originally developed for use with copper wire. Complete TTL compatible digital transceiver solutions, including the schematic, printed circuit artwork, and material lists, are presented in this application note, so that users of this low-cost fiberoptic technology do not need to do any analog design. Designers are encouraged to embed these complete fiberoptic solutions into their products and various methods for electronically downloading the reference designs are described. Why Use Optical Fibers? Copper wire is an established technology that has been successfully used to transmit data in a wide range of industrial, medical and proprietary applications, but copper can be difficult or impossible to be used in numerous situations. By using differential line receivers, optocouplers, or transformers conventional copper wire cables can be used to transmit data in applications where the reference or ground potentials of two systems are different, but during and after the initial installation great care must still be taken not to corrupt the data with noise induced into the cable’s metallic shields by adjacent power lines or differences in ground potential. Unlike copper wires, optical fibers do not require rigorous grounding rules to avoid ground loop interference, and fiberoptic cables do not need termination resistors to avoid reflections. Optical transceivers and cables can be designed into systems so that they survive lightning strikes that would normally damage metallic conductors or wire input/output I/O cards in essence, fiberoptic data links are used in electrically noisy environments where copper wire fails. In addition to all of these inherent advantages there are two other reasons why optical fibers are beginning to replace copper wires. The first reason is that training and simple tools are now available. The second reason is that when using plastic optical fiber POF , or hard clad silica HCS fiber, the total cost of the data communication link is roughly the same as when using copper wires. Wire Communication Protocols and Optical Data Links Many existing serial wire communication protocols were developed for differential line receivers or optocouplers that can sense the dc component of the data communication signal. This type of serial data is often called arbitrary duty factor data because it can remain in the logic “1” or logic “0” state for indefinite periods of time. Arbitrary duty factor data has an average value, which can instantaneously be anywhere between 0 percent and 100 percent of the binary signal’s amplitude, or in other words, arbitrary duty factor data contains dc components. Communication protocols that were developed specifically for use with copper wire often require an optical receiver that is dc coupled or capable of detecting if the data is changing from a high-to-low or low-to-high logic state. That is, the receiver needs to be an edge detector. At relatively modest data rates between zero and 10-Mbits/sec it is possible to construct dc coupled TTL-compatible fiberoptic receivers. The Avago Technologies HFBR-2521Z is a TTL-compatible, dc to 5-Mbit/sec receiver, and the HFBR-2528Z is a dc to 10-Mbit/sec CMOS or TTL-compatible receiver. Additional information about dc to 5-Mbit/ sec applications can be found in Avago Technologies AN-1035, and applications support for dc to 10-Mbit/sec applications can be obtained by reading AN-1080. This application note will focus on higher speed or higher performance arbitrary duty factor optical data communication links that work at higher data rates or greater distances than achievable with the HFBR-2521Z or HFBR- 2528Z components. The optical transceivers shown in this application note can also be used in burst-mode applications where the data is transmitted in packets and there are no transitions between bursts of date. The Pros and Cons of Arbitrary Duty Factor or Burst Mode Data The most important advantage of any existing data communication protocol is that it already exists, and typically works reasonably well with copper wires in many applications. On the other hand, existing protocols for copper wire are usually not the best choice for optimizing the performance of a fiberoptic link. For example, a receiver designed for use with arbitrary duty factor data, or burst mode data, will typically be 4 dB to 7 dB less sensitive than when the same components are used in receiver circuits optimized for use with encoded data. Encoded data normally has a 50 percent duty factor, or restricted duty factor variation, which allows the construction of higher-sensitivity fiberoptic receivers. The best arbitrary duty factor or burst-mode receivers described in this application note are considerably less sensitive than the encoded data receivers described in AN-1122. When sending arbitrary duty factor data, a separate optical link must be used to send the clock if synchronous serial communication is desired, or an asynchronous data communication system can be implemented if the data is oversampled by a local clock oscillator located at the receiving end of the fiberoptic data link. To avoid excessive pulsewidth distortion PWD , the local oscillator used to oversample the received data must operate at frequency that is greater than the serial data rate. For instance, if the data rate is 32-Mbits/sec, a clock frequency of 100 MHz will assure three times oversampling of the received serial data. As the sampling rate decreases, the PWD of the reclocked data increases. Conversely, when the sampling rate is increased, the PWD of the asynchronous data link decreases. At modest data rates such as 32-Mbits/sec the frequency of the local clock oscillator will rise sharply if higher oversampling rates are attempted for instance, to guarantee five times oversampling the clock oscillator at the receiver would need to operate at a frequency slightly greater than 160 MHz. Refer to Figure 1 for a graphical representation of the relationship between the sampling rate and PWD of an asynchronous serial data communication link. The 10Base-T copper standard sends no transitions between packets of Ethernet data, but the 10Base-FL standard for optical fiber media inserts a 1 MHz square wave between each packet of Ethernet traffic. Figure Relationship Between PWD and Sampling Rate SERIAL DATA SOURCE 32 M BITS/SEC 0% TO 100% DUTY FACTOR D.F. 32 MBd NRZ DATA fo = 16 MHz MANCHESTER ENCODER 50% EFFICIENT 50% D.F. 64 MBd ENCODED DATA fo= 32 MHz 4B5B ENCODER 80% EFFICIENT 40% TO 60% D.F. 40 MBd ENCODED DATA fo = 20 MHz 8B10B ENCODER 80% EFFICIENT 50% D.F. 40 MBd ENCODED DATA fo= 20 MHz 27 -1 SCRAMBLER 100% EFFICIENT APPROXIMATELY 50% D.F. 32 MBd ENCODED DATA fo = 16 MHz NOTE THAT Fo IS THE MAXIMUM FUNDAMENTAL FREQUENCY OF THE ENCODED DATA. THE MINMUM FUNDAMENTAL FREQUENCY OF THE ENCODED DATA IS DETERMINED BY THE ENCODER'S RUN LIMIT Figure Attributes of Encoding Burst-mode serial communication systems also have some interesting characteristics. They usually require more communication channel bandwidth, since the most common burst-mode protocols normally use a Manchester encoder, which transmits more than one symbol for each bit. Figure 2 shows how the communication channel’s bandwidth must increase when the Manchester code normally used in Ethernet data communication systems is applied to unencoded serial data. The big advantage of encoding is that it merges the clock and data so that only one communication channel is needed for both signals. In most high-performance fiberoptic communication systems, the data and clock are merged onto a single serial channel using a method that has better efficiency than Manchester encoding. Figure 2 shows several common encoding methods with better efficiency than Manchester code. Other important relationships between bits/second, and symbols/second, expressed in Baud Bd are explained by Figure Note that arbitrary duty factor unencoded data is one of the few instances when data rate in bits/second, and the symbol rate in Bd are equal. Relationships between the signaling rate expressed in Baud and the fundamental frequency of digital data communication signals are also shown in Figure Burst-mode communication protocols are used in popular serial communication systems such as Ethernet, or Arcnet. Burst-mode protocols allow many network users to share a common pair of copper conductors with a tapped connection for each user network interface. The key disadvantages of this simple tapped line architecture is that only one user can send data at any time, and a preamble must be sent to wake up or initialize the receiving node’s timing recovery circuit at the beginning of each packet of burstmode data. Burstmode, shared-wire communication links are not particularly fast, because no data can be transmitted during the preamble and each node must wait until the tapped line is quiet before data can be transmitted. Burst-mode protocols are not necessarily the best choice for optical communication links, because optical fibers are not easily and inexpensively tapped. When Ethernet traffic is sent via optical fibers, the wiring architecture is changed from a tapped serial transmission line to hubs that contain active fiberoptic transmitters and receivers. The active hubs are then connected to one another in a “star” configuration, because this star architecture is compatible with existing low-cost fiberoptic transceiver and cabling technologies. Fiberoptic receivers can be designed to accommodate burst-mode data, but it is much easier to build highsensitivity fiberoptic receivers when data is sent continuously. Continuous transmission also has other advantages. Continuous transmission increases the throughput of the LAN since there is no dead-time between packets of data. Throughput is substantially improved when data is continuously transmitted, because no time is wasted sending preambles of sufficient length to allow the receiver’s timing-recovery circuit to acquire the phase lock required to synchronously detect each serial data packet. It is interesting to note that the IEEE 10Base-FL standard for fiberoptic media uses a different transmission. The 1 MHz idle signal described in the IEEE 10Base-FL standard assures that the burst-mode protocol used for copper wire Ethernet is converted to a protocol that will optimize the performance of a fiberoptic receiver. More details about inexpensive fiberoptic solutions suitable for use with higher-efficiency block substitution codes, such as 4B5B, and 8B10B, can be found in Avago Technologies Application Notes 1122 and This publication will stay focused on solutions compatible with unencoded data, because many system designers need a fiberoptic solution that can use protocols originally developed for use with copper wires. Distances and Data Rates Achievable The simple transceivers recommended in this application note can be used to address a very wide range of distances, data rates, and system cost targets. The maximum distances allowed with various types of optical fiber when using Avago Technologies’ wide range of fiberoptic transceiver components are shown Table One simple calculation is needed to optimize the receiver for use at the desired maximum symbol rate of your system application. No transmitter or receiver adjustments are needed when using fiber cable length that vary from virtually zero length up to the maximum distances specified in Table

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Inexpensive dc to 32 MBd Fiberoptic Solutions for Industrial, Medical,Telecom, and Proprietary Data Communication Applications

Application Note 1121

Introduction

Low-cost fiberoptic data-communication links have been used to replace copper wire in numerous industrial, medical, and proprietary applications. The fiberoptic transmitter and receiver circuits in this publication address a wide range of applications. These recommended circuits are compatible with unencoded or burst-mode communication protocols originally developed for use with copper wire. Complete TTL compatible digital transceiver solutions, including the schematic, printed circuit artwork, and material lists, are presented in this application note, so that users of this low-cost fiberoptic technology do not need to do any analog design. Designers are encouraged to embed these complete fiberoptic solutions into their products and various methods for electronically downloading the reference designs are described.

Why Use Optical Fibers?

Copper wire is an established technology that has been successfully used to transmit data in a wide range of industrial, medical and proprietary applications, but copper can be difficult or impossible to be used in numerous situations. By using differential line receivers, optocouplers, or transformers conventional copper wire cables can be used to transmit data in applications where the reference or ground potentials of two systems are different, but during and after the initial installation great care must still be taken not to corrupt the data with noise induced into the cable’s metallic shields by adjacent power lines or differences in ground potential. Unlike copper wires, optical fibers do not require rigorous grounding rules to avoid ground loop interference, and fiberoptic cables do not need termination resistors to avoid reflections. Optical transceivers and cables can be designed into systems so that they survive lightning strikes that would normally damage metallic conductors or wire input/output I/O cards in essence, fiberoptic data links are used in electrically noisy environments where copper wire fails. In addition to all of these inherent advantages there are two other reasons why optical fibers are beginning to replace copper wires. The first reason is that training and simple tools are now available.

The second reason is that when using plastic optical fiber POF , or hard clad silica HCS fiber, the total cost of the data communication link is roughly the same as when using copper wires.

Wire Communication Protocols and Optical Data Links

Many existing serial wire communication protocols were developed for differential line receivers or optocouplers that can sense the dc component of the data communication signal. This type of serial data is often called arbitrary duty factor data because it can remain in the logic “1” or logic “0” state for indefinite periods of time. Arbitrary duty factor data has an average value, which can instantaneously be anywhere between 0 percent and 100 percent of the binary signal’s amplitude, or in other words, arbitrary duty factor data contains dc components. Communication protocols that were developed specifically for use with copper wire often require an optical receiver that is dc coupled or capable of detecting if the data is changing from a high-to-low or low-to-high logic state. That is, the receiver needs to be an edge detector. At relatively modest data rates between zero and 10-Mbits/sec it is possible to construct dc coupled TTL-compatible fiberoptic receivers. The Avago Technologies HFBR-2521Z is a TTL-compatible, dc to 5-Mbit/sec receiver, and the HFBR-2528Z is a dc to 10-Mbit/sec CMOS or TTL-compatible receiver. Additional information about dc to 5-Mbit/ sec applications can be found in Avago Technologies AN-1035, and applications support for dc to 10-Mbit/sec applications can be obtained by reading AN-1080. This application note will focus on higher speed or higher performance arbitrary duty factor optical data communication links that work at higher data rates or greater distances than achievable with the HFBR-2521Z or HFBR- 2528Z components. The optical transceivers shown in this application note can also be used in burst-mode applications where the data is transmitted in packets and there are no transitions between bursts of date.

The Pros and Cons of Arbitrary Duty Factor or Burst Mode Data

The most important advantage of any existing data communication protocol is that it already exists, and typically works reasonably well with copper wires in many applications. On the other hand, existing protocols for copper wire are usually not the best choice for optimizing the performance of a fiberoptic link. For example, a receiver designed for use with arbitrary duty factor data, or burst mode data, will typically be 4 dB to 7 dB less sensitive than when the same components are used in receiver circuits optimized for use with encoded data. Encoded data normally has a 50 percent duty factor, or restricted duty factor variation, which allows the construction of higher-sensitivity fiberoptic receivers. The best arbitrary duty factor or burst-mode receivers described in this application note are considerably less sensitive than the encoded data receivers described in AN-1122.

When sending arbitrary duty factor data, a separate optical link must be used to send the clock if synchronous serial communication is desired, or an asynchronous data communication system can be implemented if the data is oversampled by a local clock oscillator located
at the receiving end of the fiberoptic data link. To avoid excessive pulsewidth distortion PWD , the local oscillator used to oversample the received data must operate at frequency that is greater than the serial data rate. For instance, if the data rate is 32-Mbits/sec, a clock frequency of 100 MHz will assure three times oversampling of the received serial data. As the sampling rate decreases, the PWD of the reclocked data increases. Conversely, when the sampling rate is increased, the PWD of the asynchronous data link decreases. At modest data rates such as 32-Mbits/sec the frequency of the local clock oscillator will rise sharply if higher oversampling rates are attempted for instance, to guarantee five times oversampling the clock oscillator at the receiver would need to operate at a frequency slightly greater than 160 MHz. Refer to Figure 1 for a graphical representation of the relationship between the sampling rate and PWD of an asynchronous serial data communication link.

The 10Base-T copper standard sends no transitions between packets of Ethernet data, but the 10Base-FL standard for optical fiber media inserts a 1 MHz square wave between each packet of Ethernet traffic.

Figure Relationship Between PWD and Sampling Rate

SERIAL DATA SOURCE
32 M BITS/SEC
0% TO 100% DUTY FACTOR D.F.
32 MBd NRZ DATA fo = 16 MHz

MANCHESTER ENCODER
50% EFFICIENT
50% D.F.
64 MBd ENCODED DATA fo= 32 MHz
4B5B ENCODER 80% EFFICIENT
40% TO 60% D.F.
40 MBd ENCODED DATA fo = 20 MHz
8B10B ENCODER 80% EFFICIENT
50% D.F.
40 MBd ENCODED DATA fo= 20 MHz
27 -1 SCRAMBLER 100% EFFICIENT

APPROXIMATELY 50% D.F.
32 MBd ENCODED DATA fo = 16 MHz

NOTE THAT Fo IS THE MAXIMUM FUNDAMENTAL FREQUENCY OF THE ENCODED DATA. THE MINMUM FUNDAMENTAL FREQUENCY OF THE ENCODED DATA IS DETERMINED BY THE

ENCODER'S RUN LIMIT

Figure Attributes of Encoding

Burst-mode serial communication systems also have some interesting characteristics. They usually require more communication channel bandwidth, since the most common burst-mode protocols normally use a Manchester encoder, which transmits more than one symbol for each bit. Figure 2 shows how the communication channel’s bandwidth must increase when the Manchester code normally used in Ethernet data communication systems is applied to unencoded serial data. The big advantage of encoding is that it merges the clock and data so that only one communication channel is needed for both signals. In most high-performance fiberoptic communication systems, the data and clock are merged onto a single serial channel using a method that has better efficiency than Manchester encoding. Figure 2 shows several common encoding methods with better efficiency than Manchester code. Other important relationships between bits/second, and symbols/second, expressed in Baud Bd are explained by Figure Note that arbitrary duty factor unencoded data is one of the few instances when data rate in bits/second, and the symbol rate in Bd are equal. Relationships between the signaling rate expressed in Baud and the fundamental frequency of digital data communication signals are also shown in Figure

Burst-mode communication protocols are used in popular serial communication systems such as Ethernet, or Arcnet. Burst-mode protocols allow many network users to share a common pair of copper conductors with a tapped connection for each user network interface. The key disadvantages of this simple tapped line
architecture is that only one user can send data at any time, and a preamble must be sent to wake up or initialize the receiving node’s timing recovery circuit at the beginning of each packet of burstmode data. Burstmode, shared-wire communication links are not particularly fast, because no data can be transmitted during the preamble and each node must wait until the tapped line is quiet before data can be transmitted. Burst-mode protocols are not necessarily the best choice for optical communication links, because optical fibers are not easily and inexpensively tapped. When Ethernet traffic is sent via optical fibers, the wiring architecture is changed from a tapped serial transmission line to hubs that contain active fiberoptic transmitters and receivers. The active hubs are then connected to one another in a “star” configuration, because this star architecture is compatible with existing low-cost fiberoptic transceiver and cabling technologies. Fiberoptic receivers can be designed to accommodate burst-mode data, but it is much easier to build highsensitivity fiberoptic receivers when data is sent continuously. Continuous transmission also has other advantages. Continuous transmission increases the throughput of the LAN since there is no dead-time between packets of data. Throughput is substantially improved when data is continuously transmitted, because no time is wasted sending preambles of sufficient length to allow the receiver’s timing-recovery circuit to acquire the phase lock required to synchronously detect each serial data packet. It is interesting to note that the IEEE 10Base-FL standard for fiberoptic media uses a different transmission.

The 1 MHz idle signal described in the IEEE 10Base-FL standard assures that the burst-mode protocol used for copper wire Ethernet is converted to a protocol that will optimize the performance of a fiberoptic receiver. More details about inexpensive fiberoptic solutions suitable for use with higher-efficiency block substitution codes, such as 4B5B, and 8B10B, can be found in Avago Technologies Application Notes 1122 and This publication will stay focused on solutions compatible with unencoded data, because many system designers need a fiberoptic solution that can use protocols originally developed for use with copper wires.

Distances and Data Rates Achievable

The simple transceivers recommended in this application note can be used to address a very wide range of distances, data rates, and system cost targets. The maximum distances allowed with various types of optical fiber when using Avago Technologies’ wide range of fiberoptic transceiver components are shown Table One simple calculation is needed to optimize the receiver for use at the desired maximum symbol rate of your system application. No transmitter or receiver adjustments are needed when using fiber cable length that vary from virtually zero length up to the maximum distances specified in Table

Notice: we do not provide any warranties that information, datasheets, application notes, circuit diagrams, or software stored on this website are up-to-date or error free. The archived HFBR-0536Z Datasheet file may be downloaded here without warranties.

Datasheet ID: HFBR-0536Z 520243