ACS102A データシートの表示（PDF） - Semtech Corporation

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ACS102A

Fiber Modem

Semtech Corporation 

Advanced Communications

ACS102A Data Sheet

Single/Dual Fiber Modem for Asynchronous Data Rates from DC to 160kbps

Transmitter and Receiver Functions

Mode 4 - Single Fiber 3-pin LASER/PIN mode

This device offers one high speed and three low speed full duplex

channels to the user in a completely transparent way, appearing as

4 full duplex channels even though the medium connecting the

devices may only be a single fiber link.

Data from the TxD and low frequency channels is time

compressed in an internal FIFO and sent over the fiber link in a

Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=1

This is a single-fiber mode where the LASER is used for transmis-

sion and the monitor PIN diode within the LASER is used for

reception. Differential reception from the PIN diode is used to

maximise sensitivity. Connections are shown below :

burst within a predefined window. The device at each end of the

link automatically synchronise with each other such that the

transmit and receive windows are interleaved. The TxD input data

LASER

of the transmitting modem is also data compressed. The 3B4B

LAP

Fiber

encoding method is used for communication between ACS102As,

thus ensuring that there is no DC component in the signal. The

PINP

encoding and decoding is transparent to the user.

LAN

In the receiving modem, 3B4B encoding ensures easy extraction of

the bit-clock. The received data is filtered, decoded, and then

stored in the output memory. The memory provides time expansion,

3-pin LASER single fiber mode

de-jittering and frequency compensation functions. The data is then

decompressed and directed to the RxD output pin, appearing after a

minimal delay, in the same format as that presented at the TxD pin

Mode 5 - Single Fiber 4-pin LASER/PIN mode

at the far end.

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Operational Modes

Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=0

This is a single-fiber mode where the LASER is used for transmis-

sion and the monitor PIN diode within the LASER is used for

The ACS102A is compatible with the ACS102 but offers over twice

reception. Differential reception from the PIN diode is used to

the max data rate and incorporates the laser interface modes

maximise sensitivity. Connections are shown below :

previously associate with the ACS402. The ACS102A is a pin and

functional compatible replacement for both the ACS102 and

ACS402. The following sections detail the operating modes for all

configurations of LED, LASER and LED/PIN or LASER/PIN

combinations. Additional modes are also described for new ways of

LASER

LAP

Fiber

interfacing the device with external PIN / amplifier modules.

PINN

PINP

LED Interface Modes

LAN

Mode 1 - Single Fiber LED mode

Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=0

4-pin LASER single fiber mode

This is the operational mode for single fiber transmission with a

PPLED. The LED is used for both transmission and reception of

data over the fiber. An example circuit diagram showing the

necessary connections is shown in figure 4. This also shows an

example circuit for interfacing to the RS232 voltage levels of a PC

serial port.

Mode 2 - Dual Fiber LED/PIN mode

Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=1

This is a twin-fiber mode where the LED is used for transmission

and a separate PIN Diode is used for reception. This allows the use

of less expensive standard LEDs and PINs rather than bi-directional

PPLEDs or Duplex devices. An example circuit diagram showing

the necessary connections is shown in figure 5.

LASER Interface Modes

Mode 3 - Dual Fiber LASER/PIN mode

Setup : DP5=0, DP4=1, DP3=0, DP2=1, DP1=0

This is a twin-fiber mode where the LASER is used for transmission

and a separate PIN Diode is used for reception. An example circuit

diagram showing the necessary connections is shown in figure 6.

Differential reception from the PIN diode is used to maximise

sensitivity. Since PINP is also used for LASER current control via

monitoring of the monitor diode current, the LAP and LAN pins are

automatically floated during data reception.

Either 3 or 4 pin LASERs may be used in this mode. For 4 pin

LASERS the extra pin of the monitor diode cathode is connected

to the LASER anode, the same as it is shown in figure 6 with the

internal connection of a typical 3-pin LASER.

LASER Duplex Device Use

The Laser duplex device is composed of a 3 or 4 pin Laser for

transmission and a PIN diode for reception in a single housing.

Mode 3, as detailed previously is used for interfacing to these

devices. The Duplex devices are driven by the ACS102A in a half-

duplex manner, even though to the user it appears as a full duplex

link. As a consequence potential cross-talk between the transmit-

ter and receiver is ignored, allowing excellent performance from

low cost components.

Additional Alternative Modes

The previous modes detail the most common setups for most

typical LED, LED/PIN or LASER/PIN combinations. Many other

possible operating modes are possible via the DP1-5 pins setups.

Some of the other less common connection combinations are

shown below. These include modes for using a LASER as a

receiver as well as a transmitter in a single fiber link, where the

LASER device supports this, receiving from both the LASER and

monitor PIN, and modes for digital interfacing to external PIN/

transimpedance amplifier (TIA) modules. Only use those setups

on DP1-5 indicated in this specification, other pin combinations

may activate unpublicised functional or test modes which may lead

to damage of the LASER, where this is used.

Mode 6 - Single Fiber 4-pin LASER/PIN mode (Las & mon recv)

Setup : DP5=0, DP4=0, DP3=0, DP2=0, DP1=0

This is a single-fiber mode where the LASER is used for transmis-

sion and the LASER and the monitor PIN diode within the LASER is

used for reception. Connections are as in mode 5.

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