Application Note Interfacing the 1724-Type Microprocessor-Controlled EDFA via a Serial Communication Port Introduction The 1724-type erbium-doped fiber amplifier (EDFA) is a precision, microprocessor-controlled, fully interactive optical amplifier characterized by low power dissipation and high output power; it operates from a single 5 V power supply. The amplifier status and operation can be monitored or changed by sending proper command syntax to the amplifier via a simple 2-wire serial communication interface. This application note describes the communication protocol, both hardware and software, and the commands to instruct the 1724-type amplifier to perform desired operations. Designed for use in single-channel or video applications, the standard 1724-type EDFA incorporates a DB-25 connector and a microcontroller with TTL compatible alarm monitoring.
Interfacing the 1724-Type Microprocessor-Controlled EDFA Application Note via a Serial Communication Port Communication Description RS-232 Serial Interface Communicating with the 1724-type EDFA is accomplished through an RS-232 interface. When a microprocessor is linked directly to the device, no additional hardware is required. However, if a personal computer is linked with it via an RS-232C serial port, then a translator IC such as the Linear Technology LT1081CS is required to translate the logic levels. The 1724-type evaluation boards with all the necessary hardware to interface between a PC with a serial port and the 1724-type amplifier are available for ordering upon request. Commands and data are given in simple ASCII strings. Transmitting and receiving numerical data are in hexadecimal and decimal values. Figure 1. 1724-Type EDFA Evaluation Board 2 Agere Systems Inc.
Application Note Interfacing the 1724-Type Microprocessor-Controlled EDFA via a Serial Communication Port Communication Description (continued) Communication Setup The 1724-type amplifier serial port is set at 9600 baud, 8 data bits, no parity, and 1 stop bit. The table below describes the 1724 generic pinout (DB25 male connector). Table 1. 1724-Type EDFA Pin Description (DB25 Connector) Pin Number Description Pin Number Description 1 5 V 14 GND 2 5 V 15 GND 3 5 V 16 GND 4 5 V 17 GND 5 Reserved 18 RS-232 OUT(TTL) 6 Reserved 19 Low Input Power Alarm 7 EDFA Temperature Alarm 20 Reserved 8 Low Output Power Alarm 21 Amplifier Disable Input 9 Pumps Bias Alarm 22 RS-232 IN (TTL) 10 Pumps Temperature Alarm 23 Reserved 11 Loss-of-input Power Auto Shutdown Override 24 5 V 12 5 V 25 GND 13 GND Sending Data to the 1724-Type Amplifier Link Status Before sending a command to the 1724-type amplifier, the user must send a carriage return <cr>; the amplifier responds with a <cr>, a line feed <LF>, and a ready prompt >. This is a quick test to see if the communication link is operational, and to clear any potential data in the amplifier s RS-232 buffer. Command Sequence When sending a command to the amplifier, the user must send one character at a time and wait for an echo to come back from the amplifier before sending the next character. This sequence prevents the amplifier serial port buffer from overflowing. All commands sent to the amplifier must be terminated with a carriage return <cr>. Receiving Data from the 1724-Type Amplifier Upon receiving the <cr>, the amplifier will process the command and send back the requested information followed by a <cr><lf> and terminate with a prompt character. If the command is invalid or if the information is unavailable, only a <cr><lf> will be returned to the user, without a prompt character. Agere Systems Inc. 3
Interfacing the 1724-Type Microprocessor-Controlled EDFA Application Note via a Serial Communication Port Command Syntax DXX<cr> Command This is a public command designed to request the 1724-type amplifier to report certain amplifier parameters back to the user. Where: XX is a hexadecimal number with a value from 00 to FF, which represents the desired information to be returned. However, if D<cr> is sent without the hexadecimal numbers, the amplifier will interpret it as D00<cr>. D<cr> is designed intentionally to reduce the number of characters sent to the amplifier, since the D00<cr> command will be used most frequently to query the amplifier status. The following information is returned by the amplifier upon receiving either the D<cr> or D00<cr> command: <LF>EDFATEMP INMON OUTMON REFL ANALOGIN ALARM<cr><LF> BIAS1 TEMP1 TEC1 BD1 BIAS2 TEMP2 TEC2 BD2 BIAS3 TEMP3 TEC4 BD4 BIAS4 TEMP4 TEC4 BD4<cr><LF> Where: EDFATEMP is the amplifier internal temperature voltage. INMON, OUTMON are the input and the output tap monitor voltages, respectively. REFL, ANALOG are two parameters currently not in use and they should be ignored. ALARM is the amplifier alarm status (32-bit). BIAS1, TEMP1, TEC1, BD1, BIAS2, etc., are the pump bias current, pump temperature, TEC current, and pump backfacet current of pumps one, two, three, and four, respectively. Each parameter is separated by a space. With the exception of D or D00, all the data returned from the amplifier will be in this format: <LF>XXYY<cr><LF>. Where: XX and YY are the most and the least significant bytes, respectively. All leading zeros of XXYY are suppressed. For example, if D01 is sent, the amplifier returns a value of <LF>100<cr><LF> instead of <LF>0100<cr><LF>. 4 Agere Systems Inc.
Application Note Interfacing the 1724-Type Microprocessor-Controlled EDFA via a Serial Communication Port Command Syntax (continued) DXX<cr> Command (continued) Table 2. DXX Command Descriptions Command Description Command Description D or D00 Amplifier Status D1E Bias3 Alarm Threshold D01 Amplifier Internal Temperature D1F Bias4 Alarm Threshold D02 Input Tap Voltage D20 Reserved D03 Output Tap Voltage D21 Reserved D04 Reserved D22 Reserved D05 Reserved D23 Reserved D06 Pump1 Bias D24 Pump1 High-temperature Alarm D07 Pump2 Bias D25 Pump2 High-temperature Alarm D08 Pump3 Bias D26 Pump3 High-temperature Alarm D09 Pump4 Bias D27 Pump4 High-temperature Alarm D0A Pump1 Backfacet Current D28 TEC1 Alarm Threshold D0B Pump2 Backfacet Current D29 TEC2 Alarm Threshold D0C Pump3 Backfacet Current D2A TEC3 Alarm Threshold D0D Pump4 Backfacet Current D2B TEC4 Alarm Threshold D0E Pump1 Temperature D2C Reserved D0F Pump2 Temperature D2D Reserved D10 Pump3 Temperature D2E Reserved D11 Pump4 Temperature D2F Reserved D12 TEC1 Current D30 Reserved D13 TEC2 Current D31 Reserved D14 TEC3 Current D32 Reserved D15 TEC4 Current D33 Reserved D16 Amplifier Alarm Status (32-bit) (See D16 description, next page.) D34 Output Power Set Point (See D34 description, next page.) D17 EDFA Temperature Alarm Threshold D35 Input Power Alarm Hysteresis D18 Input Alarm Threshold D36 Output Power Alarm Hysteresis D19 Output Alarm Threshold D37 Bias Alarm Hysteresis D1A Reserved D38 TEC Alarm Hysteresis D1B Reserved D39 Temperature Alarm Hysteresis D1C Bias1 Alarm Threshold D3A Reserved D1D Bias2 Alarm Threshold D3B EDFA Temperature Alarm Hysteresis Agere Systems Inc. 5
Interfacing the 1724-Type Microprocessor-Controlled EDFA Application Note via a Serial Communication Port Command Syntax (continued) DXX<cr> Command (continued) D16 This command is a request for the amplifier alarm status, which is a 32-bit word, where: D34 Bit 0 Low Output Power Alarm Bit 1 Low Input Power Alarm Bit 2 EDFA Temperature Alarm Bit 3 Reserved Bit 4 Bias1 Alarm Bit 5 Bias2 Alarm Bit 6 Bias3 Alarm Bit 7 Bias4 Alarm Bit 8 Pump 1 High-temperature Alarm Bit 9 Pump 2 High-temperature Alarm Bit 10 Pump 3 High-temperature Alarm Bit 11 Pump 4 High-temperature Alarm Bit 12 TEC 1 Current Alarm Bit 13 TEC 2 Current Alarm Bit 14 TEC 3 Current Alarm Bit 15 TEC 4 Current Alarm Bit 16 Reserved Bit 17 Reserved Bit 18 Reserved Bit 19 Reserved Bit 20 Reserved Bit 21 Reserved Bit 22 Amplifier Disable Status Bit 23 Reserved Bits 24 to 31 are not used For EDFAs that are configured for DWDM applications, this value represents the output power set point when the EDFA has all input channels populated. 6 Agere Systems Inc.
Application Note Interfacing the 1724-Type Microprocessor-Controlled EDFA via a Serial Communication Port Command Syntax (continued) Conversion Factors The following sections describe the formulas to convert the value reported from the 1724-type amplifier to its proper value unit. Before using the conversion factor, ADCHEX value will be converted to ADCDEC and then be converted to its true voltage: Parameter voltage = Reference voltage ADCDEC ----------------------------------------------- 1024 For example, a value of 1F4HEX is returned from the 1724-type amplifier. This value is equivalent to 500DEC. If the amplifier s reference voltage is 2.502 V, use the formula above; the equivalent voltage is: Pump Bias Current 1.22 V = 500 2.502 -------------- 1024 Pump bias current = ( Bias voltage) A V --- TEC Current TEC current = ( TEC voltage) A V --- Backfacet Current Backfacet voltage Backfacet current = ---------------------------------------------- A 2000 --- V Pump Temperature where: a = 1.1299 3 b = 2.3405 4 cc = 8.759 8 r 30100 * VTEMP = ------------------------------------- 2.5 VTEMP Pump temperature ( C) = 1 --------------------------------------------------------------------------- 273.16 a + ( b * Ln(r) ) + cc * [ Ln() r 3 ] Input and Output Tap Monitor Voltages The tap monitor voltages are the same as the parameter voltage. Amplifier Internal Temperature Ampliier internal temperature ( C) = VEDFATEMP 0.5 ---------------------------------------------- 0.01 Agere Systems Inc. 7
Interfacing the 1724-Type Microprocessor-Controlled EDFA Application Note via a Serial Communication Port SAAXXYY<cr> Command Although the output power and all required alarm levels are preset and tested at the factory, sometimes the customers may want to make some minor adjustment to fit their needs. The S command is used to customize the 1724-type amplifier output power and input and output alarms to their system needs. Where: AA is the parameter to be changed and XXYY is the new data. XX and YY represent the most and the least significant bytes respectively. The new value will be checked by the 1724-type amplifier to determine whether it is within the allowable range. A 1 is returned if the value is accepted, otherwise a 0 is returned. These values are not saved in the amplifier s nonvolatile memory. Therefore, they are lost when the amplifier is turned off. Table 3. SAAXXYY<cr> Command Descriptions Command S00XXYY* S01XXYY S02XXYY Output Power. Input Alarm Threshold. Output Alarm Threshold Description * S00XXYY is used to change the output power. The typical allowable range is +0.5 db to 2 db. WX<cr> Command This is a public command where X is any digit from 0 to 4. This command is designed to report the amplifier identification and its exact voltage reference value. Table 4. WX<cr> Command Descriptions Command Description W or W0 This will display the amplifier identification such as its product number, serial number, voltage reference value, firmware serial number, etc. The user should reserve a buffer of at least 1000 bytes to store the information that returns from the 1724-type amplifier. W1 Report voltage reference value. Four digits long, for example, 2504. W2 Report firmware serial number. Eight characters long, for example, C1724WDM W3 Report firmware revision number. Five characters long maximum, for example, 7.1L. W4 Report firmware date, for example, 10/01/96. For additional information, contact your Agere Systems Account Manager or the following: INTERNET: http://www.agere.com E-MAIL: docmaster@agere.com N. AMERICA: Agere Systems Inc., 555 Union Boulevard, Room 30L-15P-BA, Allentown, PA 18109-3286 1-800-372-2447, FAX 610-712-4106 (In CANADA: 1-800-553-2448, FAX 610-712-4106) ASIA: Agere Systems Hong Kong Ltd., Suites 3201 & 3210-12, 32/F, Tower 2, The Gateway, Harbour City, Kowloon Tel. (852) 3129-2000, FAX (852) 3129-2020 CHINA: (86) 21-5047-1212 (Shanghai), (86) 755-25881122 (Shenzhen) JAPAN: (81) 3-5421-1600 (Tokyo), KOREA: (82) 2-767-1850 (Seoul), SINGAPORE: (65) 6778-8833, TAIWAN: (886) 2-2725-5858 (Taipei) EUROPE: Tel. (44) 7000 624624, FAX (44) 1344 488 045 Agere Systems Inc. reserves the right to make changes to the product(s) or information contained herein without notice. No liability is assumed as a result of their use or application. Agere, Agere Systems, and the Agere logo are trademarks of Agere Systems Inc. Copyright 2002 Agere Systems Inc. All Rights Reserved AP02-097OCN (Replaces AP99-020LWP)