# How to interface a microcontroller to fibre optic?

O

#### Oliver Faust

Jan 1, 1970
0
Hi,
I'm new to hardware designs with fibre optics. My application is
relative simple, I want to network embedded processors using fibre
optics as physical layer. At the moment I'm using RS232 for point to
point connections. To increase the data-rate and to have better
protection against EMI interference, I want to replace the electrical
wires with optical fibres.
My application is point to point. The data-rate is not fixed yet,
however it should be somewhere between 25 and 150Mb/s. Therefore,
plastic fibres should be sufficient. At the moment I'm struggling to
find appropriate interface chips which provide the UART or NIC
functionality for fibre optics on one side and a microcontoller
interface at the other. Here is a small block diagram:
MC <-> NIC <<->> EO <=> EO <<->>NIC <-> MC
where
MC microcontroller
<-> Microcontroller interface (SPI, Parallel, ...)
NIC gluelogic
<<->> Electrical interface
EO electrical to optical transceiver
<=> fibre optics.

Here are my questions:
fibre optics?
What are appropriate glue logic chips which provide the NIC'
functionality?

Oliver Faust

J

#### J.A. Legris

Jan 1, 1970
0
Hi,
I'm new to hardware designs with fibre optics. My application is
relative simple, I want to network embedded processors using fibre
optics as physical layer. At the moment I'm using RS232 for point to
point connections. To increase the data-rate and to have better
protection against EMI interference, I want to replace the electrical
wires with optical fibres.
My application is point to point. The data-rate is not fixed yet,
however it should be somewhere between 25 and 150Mb/s. Therefore,
plastic fibres should be sufficient. At the moment I'm struggling to
find appropriate interface chips which provide the UART or NIC
functionality for fibre optics on one side and a microcontoller
interface at the other. Here is a small block diagram:
MC <-> NIC <<->> EO <=> EO <<->>NIC <-> MC
where
MC microcontroller
<-> Microcontroller interface (SPI, Parallel, ...)
NIC gluelogic
<<->> Electrical interface
EO electrical to optical transceiver
<=> fibre optics.

Here are my questions:
fibre optics?
What are appropriate glue logic chips which provide the NIC'
functionality?

Oliver Faust

The following book is a good starting point:

http://www.lvr.com/eec.htm

O

#### Oliver Faust

Jan 1, 1970
0
The following book is a good starting point:

http://www.lvr.com/eec.htm

Thank you for this quick response. However, the book, you link to,
does not specifically talk about fiber optics. The only interesting
chapter might be chapter 2 (Building a Network: Hardware Options). The
protocol side of my project is well defined, the network is already up
and running. At the moment, my difficulty is to get glue logic chips
which interface the microcontroller to fiber optics. For example, a
suitable technology would be fiber channel (FC) on the optical side.
However, this technology is to fast for my application (slowest FC
data rate 1Gb/s). My question is: Is there a standard way of
transferring data over an optical link at rates of about 100Mb/s? With
standard way, I mean there should be IP cores or interface chips which
implement this optical transfer standard (protocol).

Oliver

E

#### Eeyore

Jan 1, 1970
0
Oliver said:
Hi,
I'm new to hardware designs with fibre optics. My application is
relative simple, I want to network embedded processors using fibre
optics as physical layer. At the moment I'm using RS232 for point to
point connections. To increase the data-rate and to have better
protection against EMI interference, I want to replace the electrical
wires with optical fibres.
My application is point to point. The data-rate is not fixed yet,
however it should be somewhere between 25 and 150Mb/s. Therefore,
plastic fibres should be sufficient. At the moment I'm struggling to
find appropriate interface chips which provide the UART or NIC
functionality for fibre optics on one side and a microcontoller
interface at the other.

8051 family devices have a UART that in one mode will run at 1 Mbps with
as 12MHZ clock crystal.

Here is a small block diagram:
MC <-> NIC <<->> EO <=> EO <<->>NIC <-> MC
where
MC microcontroller
<-> Microcontroller interface (SPI, Parallel, ...)
NIC gluelogic
<<->> Electrical interface
EO electrical to optical transceiver
<=> fibre optics.

Here are my questions:
fibre optics?
What are appropriate glue logic chips which provide the NIC'
functionality?

proprietary.

Graham

E

#### Eeyore

Jan 1, 1970
0
Oliver said:
Thank you for this quick response. However, the book, you link to,
does not specifically talk about fiber optics. The only interesting
chapter might be chapter 2 (Building a Network: Hardware Options). The
protocol side of my project is well defined, the network is already up
and running. At the moment, my difficulty is to get glue logic chips
which interface the microcontroller to fiber optics. For example, a
suitable technology would be fiber channel (FC) on the optical side.
However, this technology is to fast for my application (slowest FC
data rate 1Gb/s). My question is: Is there a standard way of
transferring data over an optical link at rates of about 100Mb/s? With
standard way, I mean there should be IP cores or interface chips which
implement this optical transfer standard (protocol).

At 100 Mbps to an embedded controller ?

Graham

A

#### [email protected]

Jan 1, 1970
0
Hi,
I'm new to hardware designs with fibre optics. My application is
relative simple, I want to network embedded processors using fibre
optics as physical layer. At the moment I'm using RS232 for point to
point connections. To increase the data-rate and to have better
protection against EMI interference, I want to replace the electrical
wires with optical fibres.

Uhm, are you working on circuits that have to work on a neutron star?

P

#### [email protected]

Jan 1, 1970
0
Here are my questions:
fibre optics?
What are appropriate glue logic chips which provide the NIC'
functionality?

Oliver Faust

I have used the Hirschmann simple RS232 to optical adaptors in the
long ago past:
http://www.electroustic.co.uk/fibre.htm
Saves time

O

#### Oliver Faust

Jan 1, 1970
0
Usb can do that.

How far do you have to go? RS422? How complicated does it have to be I think
you can getaway with twisted pairs.

Bob

RS422 is another possible link standard which I consider for the
network links. However, for some applications RS422 is not suitable.
For example, in a very noisy (EMI) environment, such as cars or radio
applications, fiber optics have a clear advantages. In any case, the
project I'm working on should demonstrate that it is possible to build
a network of embedded processors with fiber optics as physical layer
executing our RTOS.

Oliver Faust

O

#### Oliver Faust

Jan 1, 1970
0
Dear Graham,
8051 family devices have a UART that in one mode will run at 1 Mbps with
as 12MHZ clock crystal.
This is one of my problems, from what I have read a simple UART can't
be used for fiber optic transmission. As far as I know there is no
optical transport layer for the UART protocol, there is just RS232,
RS422 and RS485. A problem I can forsee for when using a UART and an
Electrical to Optical transceiver is that the UART signal is not DC
free. Standards like Fiber Channel (FC) ensure ensure that the signal
over optical link is DC free via 8/10 encoding.
proprietary.
If I understand this right, this comes down again to use a wire
standard (UART) for optical transmission. I still wonder whether or
not this is possible.

Oliver Faust

O

#### Oliver Faust

Jan 1, 1970
0
At 100 Mbps to an embedded controller ?

Graham
This is nothing unusual, many embedded processors demo boards come
with a 100Mb/s Ethernet connection. At the moment, building up the
processor network with fiber optics is just a feasibility study. The
link speeds mentioned above are such that they can be handled by
plastic fibers, which keeps the cost down.

O

#### Oliver Faust

Jan 1, 1970
0
I have used the Hirschmann simple RS232 to optical adaptors in the
long ago past:
http://www.electroustic.co.uk/fibre.htm
Saves time

Thank you for the suggestion, but I'm interested in an embedded
solution. The plan is to manufacture a small board with a
include RS232 and optical.

Oliver Faust

J

#### Jasen Betts

Jan 1, 1970
0
Thank you for this quick response. However, the book, you link to,
does not specifically talk about fiber optics. The only interesting
chapter might be chapter 2 (Building a Network: Hardware Options). The
protocol side of my project is well defined, the network is already up
and running. At the moment, my difficulty is to get glue logic chips
which interface the microcontroller to fiber optics. For example, a
suitable technology would be fiber channel (FC) on the optical side.
However, this technology is to fast for my application (slowest FC
data rate 1Gb/s). My question is: Is there a standard way of
transferring data over an optical link at rates of about 100Mb/s? With
standard way, I mean there should be IP cores or interface chips which
implement this optical transfer standard (protocol).

If it's point-to-point you don't need a network layer.

O

#### Oliver Faust

Jan 1, 1970
0
Thank you for the suggestion, but I'm interested in an embedded
solution. The plan is to manufacture a small board with a
include RS232 and optical.

Oliver Faust

I guess you could use tcpip.

Bob

Yes, we use TCP/IP packets to carry packets from our operating system.
In this case, TCP/IP is included for compatibility rather then for
functionality reasons. The TCP/IP stack is necessary to communicate
with windows or posix sockets. And for other applications such as web
servers. However, for embedded systems even the code size of the uIP
TCP/IP stack (~5kB) is an issue.
If such applications are not considered the TCP/IP stack is not
needed. The operating system (OpenComRTOS) routes the packets.

J

#### Jörg Schneide

Jan 1, 1970
0
Oliver said:
Hi,
[..]
Here are my questions:
fibre optics?
What are appropriate glue logic chips which provide the `NIC'
functionality?

Oliver Faust

Take a look at SERCOS, MOST and ByteFlight, Wikipedia is a starting point.

Byteflight seems to be dead, so it might be difficult to get the components
now or in the future.
MOST might have a future, but I have not seen much components.
Some optical components for SERCOS are available at Digi-Key,
this may be a hint that it is active.

Jörg.

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