OPTILAB BCB-4 User manual

BCB-4 User’s Manual
Automatic Bias Controller Board, Five Mode Operation
Caution: The user must read this manual before operating the BCB-4 unit.
Operations other than those described in this manual may result in personal
injury and/or damage to the unit.
Note that any attempt to open or fix the equipment without prior approval by
Optilab, LLC voids the warranty.
Ver. 1.5
August 18, 2022

BCB-4 User’s Manual
Page ii of iii
Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
Revision History
VERSION
DATE
SUMMARY
0.1
06/12/2020
Manual introduced.
1.0
08/13/2020
Manual Released.
1.1
09/01/2020
Added manual bias mode.
1.2
10/15/2020
Added Vpi measurement function.
1.3
03/15/2021
Specification Modified
1.4
04/26/2022
Added information for setting Vpi or using a
feedback loop.
1.5
08/18/2022
Modified command set
Copyright ©2022 by Optilab, LLC
All rights reserved.
This document is copyrighted property of Optilab, LLC. It may not be used in whole or in part
for manufacture, sale, or design of items without the written permission of Optilab, LLC.
Information herein is preliminary and subject to change without any notices.

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
Tableof Contents
1. GENERAL INFORMATION 1
1.1 INTRODUCTION 1
1.2 PRODUCT OVERVIEW 1
1.3 FEATURES 1
1.4 USER SAFETY 1
2. OPERATION 2
2.1 INTRODUCTION 2
2.2 INITIAL INSPECTION 2
2.3 CONTROLS 3
2.4 APPLICATION BLOCK DIAGRAM 4
2.5 OPERATION INSTRUCTIONS 5
2.6 RS485 COMMAND SET 7
2.7 BIAS CONTROL POINT SETTING INFORMATION 7
3. TROUBLESHOOTING 8
4. TECHNICAL SPECIFICATIONS 9
5. MECHANICAL SPECIFICATIONS 9
6. SERVICE AND SUPPORT 10
6.1 WARRANTY 10
6.2 SERVICE AND CALIBRATION 10
6.3 CARE OF FIBER-OPTIC CONNECTORS 11
APPENDIX A –4-PIN MOLEX CONNECTOR 12
APPENDIX B –RS485 COMMAND SET 13

BCB-4 User’s Manual
Page 1 of 14
Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
1. General Information
1.1 Introduction
This manual contains information on the installation and operation of the BCB-4
bias controller board module unit.
1.2 Product Overview
The Optilab BCB-4 is a compact bias control board designed to maintain the
linear operating point of optical intensity modulators. Featuring a compact
miniature design for OEM integration, the BCB-4 allows for a stable Q+, Q-,
Min, and Max operation over long periods of time. The BCB-4 also features a
manual bias mode with a stable setting range of -11 to +11V DC. With a
single +5V DC power and RS-485 multi-addressing control and monitor
interface, the BCB-4 unit is the ideal choice for industrial and OEM
applications when paired with any of Optilab’s wide variety of optical
modulators, contact Optilab for more information.
1.3 Features
•Q+, Q-, Min, Max, and manual bias setting modes
•Single +5V DC power
•Compatible with all MZI optical modulators
•On-board photodiode for external optical tap (optional)
•RS-485 communication for easy control and monitoring
1.4 User Safety
1. The BCB-4 unit operates with optical modulator products that utilize invisible
light (IR). Avoid direct exposure to skin and eyes.
2. The user should never modify the PCB component; any attempt will void the
warranty and may result in electric shock and EMS attack to equipment in
the vicinity.
3. The user should avoid using any solvent or vaporizing chemical to clean the
components; it may result in damage to the surface and circuits.

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
2. Operation
2.1 Introduction
This chapter describes how to operate the BCB-4 unit and discusses the
location and function of the controls and connectors.
2.2 Initial Inspection
Your BCB-4 unit was carefully inspected before it left the manufacturer. It
should be in proper working order upon receipt. You should, however, inspect
the unit for any damage that may have occurred in transit. If the shipping
container or the packing material is damaged, keep it until the contents of the
shipment have been checked to be free of mechanical and electrical damages.
Notify Optilab, LLC promptly if any notable damage is found.
Each BCB-4 shipment should include the following:
•BCB-4 module unit
•User Manual
•Test Data
•Calibration Data (if ordered with PD)
•Optilab power/com interface module
•6 pin power/com interconnect cable
•2 pin bias interconnect cable
•4 pin power interconnect cable
•USB Cable
Optional accessories:
•Optilab PS-5-M, ±5V DC power supply

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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
2.3 Controls
FEATURE
FUNCTION
POWER/COM CABLE
CONNECT PORT
This port supplies DC power and allows the user remote control access
via RS-485, please see section 2.5 of this manual for more information.
Connector Model: JST S6B-ZR; Mating Connector: JST ZHR-6
PROGRAMMING HEADER
Internal use only
RESET BUTTON
This button is utilized to reset the internal automatic bias locking
algorithm; if the bias feature is not locking properly, pressing this button
will reset this feature for proper operation.
ONBOARD
PHOTODETECTOR
(OPTIONAL)
This photodiode works in conjunction with a tap coupler to provide
feedback of the output signal of the modulator.
DITHER SIGNAL ADJUST
This potentiometer adjustments the 1 kHz dither signal from
approximately 0 to 450 mV p-p.
BIAS OUTPUT PORT
This two-pin port is used to relay the corresponding DC bias out to the
modulator. Details on the pin-out are noted in section 2.5 of this manual.
Connector Model: JST B2B-ZR; Mating Connector: JST ZHR-2
FEATURE
FUNCTION
RS-485 CONNECTION
PORT
Connection of this port to the BCB-4 provides power to the unit and
remote control of the device via RS-485 protocol.
DC MOLEX PORT
Connect this port either the Optilab PS-5 power supply (with the provided
Molex cable), or to the appropriate +5VDC, -5VDC, GND terminals. The
pin out diagram is noted in Appendix A at the end of this manual. The
Power LED will enable when the proper connection and supply is made.
USB PORT
This port connects to any standard PC interface to allow for the remote
access and feature adjustment options.
1
2
BCB-4
4
3
5
6
Power/COM Interface Module
1
2
3

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
2.4 Application Block Diagram
The following block diagram denotes the typical connection of the BCB-4 to
increase the understanding to the end user on its operation and
interconnectivity. The BCB-4 bias controller utilizes an on-board photodetector
power monitor. In this monitor / feedback fashion, the automatic bias control
circuit (BCB-4) is used to ensure the modulator bias point is maintained at the
desired level.

BCB-4 User’s Manual
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600 E. Camelback Road, Phoenix, AZ 85012
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2.5 Operation Instructions
Start-up Procedure
To assist with connections, please see the pin out diagram below for the
BCB-4:
Unit: mm
1. Ensure that the DC bias and ground ports are securely connected to the
intensity modulator at all times.
2. Use an optical tap coupler on the output port of the intensity modulator to
provide optical feedback to the PD of the BCB-4. Without this connection the
BCB-4 will not function properly. The split ratio of the tap coupler should be
selected based on the optical input power to the intensity modulator and the
modulators insertion loss and should be between -20 and -10 dBm when the
modulator is biased to maximum point.
NOTE: An optical feedback loop is recommended for proper operation of the
BCB-4 device. This feedback loop will allow the device to measure the Vpi of
the connected modulator and allow for proper biasing. Alternatively, if a
feedback loop is not used, the Vpi value can be set manually, please refer to
the Remote-Control section of this manual for setting this value.

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
3. Make all necessary electrical connections including:
•BCB-4 bias port to modulator bias pins using the provided 2-pin cable.
•BCB-4 power/COM port to interface module RS-485 port using the
provided 6-pin cable.
•Interface module Molex connection to power supply using the provided
4-pin Molex cable.
•Interface module USB port to PC USB port using the provided USB
cable.
4. Apply PM CW laser to the intensity modulator.
5. To change the bias control point between Q+, Q-, Min, Max, or manual
mode, please refer to the Remote-Control Procedure located in the latter
portion of this section.
6. The BCB-4 unit is now fully operational; however, it may take 60 to 90
seconds for the bias controller to accurately adjust to the desired bias point
setting.
Dither Amplitude Adjustment Procedure
Utilizing the potentiometer marked in the diagram in section 2.3 of this manual,
rotate this adjustment knob to increase or decrease the dither amplitude value,
from approximately 20 to 450 mVpp. This dither signal can be measured at the
test point on the PCB marked ‘Dither’. The dither frequency of 1 kHz is fixed
and cannot be adjusted. The dither amplitude should be approximately 2% to
5% of the intensity modulators bias port Vpi. For MIN mode operation, a smaller
dither signal ~1% or lower is required to achieve high extinction ratio.
Remote Control Procedure
1. In order to offer full remote control, and to set the internal BCB-4 bias setting
mode, you will need to set up an appropriate PC, with an appropriate serial
port communication protocol software installed. You will also need to ensure
that the appropriate RS485 drivers are installed to match your operating
system of choice.
2. Once the drivers have been installed, connect the BCB-4 to a USB port on
the desired computer. The BCB-4 device should be recognized as a COM
port device under the Device Manager. If it is not recognized, then you will
need to locate the appropriate driver first in step one and repeat.

BCB-4 User’s Manual
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3. Once the BCB-4 is recognized by the PC interface, you are now ready to
send the remote commands to the BCB-4. The device uses the following
serial port communication protocols, ensure that your serial port
communication program is set appropriately:
Baud Rate: 9600 bps
Data Bits: 8
Stop Bits: 1
Parity: None
Flow Control: None
Text Transmission: Append CR, LF
2.6 RS485 Command Set
When the electrical connections have been made, and the software settings for
serial port transmission are set correctly, you are now able to send commands
to the BCB-4 module.
Please refer to Appendix B at the end of this manual for command set and the
layout of the return from the READ command.
2.7 Bias Control Point Setting Information
For setting the bias control point of the BCB-4 controller, the choices are MAX,
MIN, Q+, and Q-, please refer to the diagram below. For pulsed applications,
use the MIN point, for maximum output power, use the MAX point, and for
typical RF over fiber applications, use Q+ or Q- to minimize the 2nd and 3rd
order distortion harmonics.

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
3. Troubleshooting
SYMPTOM
POSSIBLE CAUSE AND SOLUTION
UNIT NOT BIASING
CORRECTLY
C: Improper bias pin connection setting.
S: Check to ensure that the cable between the BCB-4 and the
intended optical modulator is made correctly.
C: Optical input to the modulator is too high/low.
S: Due to the photodiode feedback design, the ability to bias the
modulator depends on the amount of photodiode current
feedback to the BCB-4. If the feedback power is greater than -10
dBm, it may saturate the BCB-4 photodiode current
measurement. If it is lower than -20 dBm, then the feedback
strength may be insufficient.
C: Onboard photodiode input is too high/low.
S: Ensure that the optical input level through the tap port is
between -20 dBm and -10 dBm for optimum performance.
C: Improper polarization input to modulator.
S: Check the input polarization type and axis alignment of your
modulator and confirm the input seed source is matching. An
improper optical input axis alignment will render the BCB biasing
(especially minimum mode) insufficient.
C: No feedback loop and/or Vpi value is set incorrectly.
S: If using a feedback loop, the Vpi programmed DAC value must
be set to 00000. If not using a feedback loop, the Vpi DAC value
should be calculated and programmed to the unit. Refer to
Appendix B of this manual for calculating and/or setting the Vpi
DAC value.
UNIT DOES NOT POWER
UP.
C: Improper power connection.
S: Please ensure that 6-pin power/com and 4 pin Molex cables
are connected properly and not damaged. Please refer to
Appendix A at the end of this manual for proper wiring if the 4-pin
Molex connector.
INCORRECT BIAS POINT
SETTING
C: Improper software bias point setting
S: Connect to the BCB-4 via the RS232 setting, and check the
current bias point setting, and make adjustment accordingly.

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
4. Technical Specifications
Optical Input Requirements
Operating Wavelength
980nm –1700nm
Optical Input Level (onboard PD)
-20 dBm minimum, -10 dBm max.
RF / DC Bias Specifications
Dither Signal Frequency
1 kHz
Dither Adjustment Range
20 to 450 mVpp
Bias Modes Available
Q+, Q-, Minimum, Maximum, and
Manual Bias
DC Bias Output Voltage Range
-10V to +10V
Modulator Voltage Vpi Range
1.5 to 8V
5. Mechanical Specifications
Power Supply Requirements
+5VDC, 100mA max
Optical Connector (Optilab
photodiode option)
FC/APC Standard, additional types
available
Operating Temperature
-10°C to +60°C
Storage Temperature
-55°C to +85°C
Control
Dither frequency adjust, bias mode
adjust (Q+, Q-, Min, Max)
Dimensions (mm)
27.5 x 85.0 x 16.9 (see drawing
below)

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
6. Service and Support
6.1 Warranty
Optilab, LLC guarantees its BCB-4 unit to be free of defects for 1 year from the
date of shipment. The guarantee does not cover any damages resulting from
the misuse or improper handling of the equipment, or any incidental or
consequential loss. Note that the warranty will be void upon any attempt to
open or to fix the equipment by the user without prior approval of Optilab, LLC
6.2 Service and Calibration
Your BCB-4 unit has been designed to provide years of trouble-free operation.
No internal maintenance is required provided that the equipment is properly
handled, operated, and kept away from contamination. For any questions
regarding the operation and performance of the unit, please contact Optilab,
LLC at:
Optilab, LLC
600 E. Camelback Road
Phoenix, AZ 85012
Phone: [phone]
Fax: [phone]
Email: [email protected]

BCB-4 User’s Manual
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Optilab, LLC
600 E. Camelback Road, Phoenix, AZ 85012
Phone: [phone], Fax: [phone], Email: [email protected]
6.3 Care of Fiber-optic Connectors
Damage to optical connectors account for more than 70 percent of equipment
performance degradation. To avoid such damage, the user should use only industrial
grade 99% pure isopropyl alcohol and follow the procedures below to keep the
connectors, adaptors, and receptacles clean.
Cleaning Optical Connector End-face with Wipe and Alcohol
To properly clean optical connectors utilizing lens tissue grade wipes and alcohol
follow the procedure below. The moist wipe removes dust particles, oil and
contaminants that may damage or blot the end-face of the connector during
connection. The dry wipe removes residual alcohol that may be ignited by optical
emission.
1. Disable the optical output and turn off unit to prevent accidental exposure or
damage to the optical connector by optical emission.
2. Moisten a wipe with alcohol by placing on top of the alcohol dispenser and push
down to saturate the wipe.
3. Place the moist wipe on a work surface and place a second dry wipe next to it.
4. Wipe the optical connector, end-face down on the moist wipe 3 times and then
repeat on the dry wipe.
5. Visually inspect the end-face of the optical connector with an optical microscope to
verify cleanliness. Repeat steps 2 to 5 as needed.
Cleaning Optical Connector Sides, Receptacles, Adaptors with Swab and Alcohol
Dust or particles can adhere to the insides of receptacles and adaptors or the sides of
the optical connector ferrule. Their presence can affect the alignment of the optical
fiber connectors and increase connection loss. To properly clean optical connectors,
receptacles, and adaptors utilizing a swab and alcohol follow the procedure below:
1. Disable the optical output and turn off unit to prevent accidental exposure or
damage to the optical connector by optical emission.
2. Moisten the swab by placing it on top of the alcohol dispenser and push down to
saturate the swab.
3. For receptacles, adapters, or other connection points, insert the moistened swab
and rotate the tip 1/2 turn clockwise and counterclockwise 6 times while applying
light but firm pressure.
4. For fiber connectors, rotate the tip of the moistened swab 5 revolutions around the
connector while applying light but firm pressure.
5. Visually inspect the end face of the connector with an optical microscope to verify
cleanliness. Clean end-face as needed.

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Phone: [phone], Fax: [phone], Email: [email protected]
Appendix A –4-pin Molex Connector
NOT USED FOR BCB-4

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Phone: [phone], Fax: [phone], Email: [email protected]
Appendix B –RS485 Command Set
[ADD] Refers to address programmed to the device using the SETADD:X command and should be replaced with
this address when sending commands to the device.
{CR/LF} Refers to the type of termination used to signal the end of a command being sent to the device. This
should be handled by your communication software and not manually typed into the command.
QUERY COMMANDS
READ[ADD]V{CR/LF} –Reads the bias voltage DAC value
READ[ADD]VPI{CR/LF} –Read the Vpi DAC value
READ[ADD]S{CR/LF} –Read the device information (see return format below)
110373
Optical Input DAC Value
The optical input DAC value is a representation of the optical input power to the feedback photodiode. If your unit
was ordered with the photodiode installed, the calibration data for the PD has been provided for you. You can
calculate the optical power using the following formula:
Optical Power Coefficient xDAC Value =Optical Power (μW)
Bias Voltage DAC Value
The bias voltage DAC value is a representation of the actual voltage. You can calculate the bias voltage and/or the
DAC value using the formulas below.
VMAX -(Voltage Coefficient xDAC Value) =Voltage (V)
or
(VMAX -Voltage) / Voltage Coefficient = DAC Value
Vpi Voltage DAC Value
The Vpi voltage DAC value is a representation of the actual voltage. You can calculate the Vpi voltage and/or the
DAC value using the formulas below.
Voltage Coefficient xDAC Value =Vpi (V)
or
Vpi (V) / Voltage Coefficient = DAC Value
DEVICE
ADDRESS
BIAS MODE
SEE TABLE BELOW
OPTICAL INPUT
DAC VALUE

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SET COMMANDS
RESET[ADD]{CR/LF} –Resets the device.
SETADD:X{CR/LF} –Set the device address for RS-485 communication. Range: 0 –9. Default: 1.
Example: SETADD:1{CR/LF} –Sets the device address to 1.
SET[ADD]M:X{CR/LF} –Set the device bias mode (see table below); 1 digit required.
Example: SET2M:1{CR/LF} –Sets the bias mode to Q+ for the device at address 2.
MODE #
BIAS MODE
1
Q+
2
Q-
3
MAX
4
MIN
5
Manual Bias
SET[ADD]V:XXXXX{CR/LF} –Set the bias voltage DAC value when the device is in manual bias mode (5).
Range: 00000 –16383 (00000 ≈ 11.00V and 16383 ≈ -11.00V).
5 digit field width required, pad with zeros on left.
Example: SET1V:00000{CR/LF} –Sets the bias voltage to about +11.00V for the device at address 1.
SETOFS[1/2/3/4]:+/-XX{CR/LF} –Set the correction value of the readback DAC value for each bias mode.
Range: ±00 –99; digit before the colon corresponds to the bias mode (see chart above).
Sign is required; 2-digit field width required, pad with zeros on left.
Example: SETOFS1:+09{CR/LF} –Sets the correction value to +09 for bias mode 1 (Q+).