850 - 1550nm Electro Optic Light Modulators

850nm To 1550nm Electro Optic Light Modulators

SCQ series electro-optic modulators have the features of low insertion loss, wide bandwidth, low half-wave voltage etc and are to be used in space optical communication, time base, pulse generator and quantum optics etc.

SCQ series electro-optic modulators are mainly divided into two groups: intensity modulators and phase modulators. Their working wavelengths are 780nm, 850nm, 1064nm, 1310nm, 1550nm and 2000nm.Other wavelengths are available upon request.

Definition of Part Numbers: SCQ-XX-WW-XG-F-FC

• XX: modulator type. AM is intensity modulator and PM is phase modulator.

• WW: operation wavelength, such as 850nm, 1064nm, 1310nm,1550nm and 2000nm

• XG: operation bandwidth, such as 2.5G, 10G, 40G

• F: In-out fiber such as PP (PM/PMF)

• FC: fiber connector such as FA (FC/APC), FP (FC/PC)

1. SCQ Series Intensity Modulators

1.1 SCQ-AM-1310 Series 1310nm Intensity Modulators

The LiNbO3 intensity modulator is widely used in high-speed optical communication system, laser sensing and ROF systems because of well electro-optic effect. The SCQ-AM series based on MZ structure and X-cut design, has stable physical and chemical characteristics, which can be applied both in laboratory experiments and industrial systems.

Features:

• Low insertion loss

• Bandwidth: 2.5GHz

• Low half-wave voltage

• Customization option

Applications:

• ROF systems

• Quantum key distribution

• Laser sensing systems

• Side-band modulation

Optical Parameters:

Electrical Parameters:

Limit Conditions:

Order Information:

2. SCQ Series Phase Modulators

2.1 SCQ-PM Series 1310nm Electro-optical Phase Modulators

The LiNbO3 phase modulator is widely used in a high-speed optical communication system, laser sensing, and ROF systems because of well electro-optic effect. The SCQ-PM-1310 series, based on Ti-diffused technology, has stable physical and chemical characteristics, which can meet most applications in laboratory experiments and industrial systems.

Features:

• Low insertion loss

• Polarization-maintaining

• Low half-wave voltage

• Dual-polarization option

Application:

• Optical communication

• Quantum key distribution

• Frequency shifting

Optical parameters:

Electrical Parameters:

Limit parameters:

Ordering Information:

3. Drivers

3.1 SCQ-RF Series Drivers

SCQ-RF broadband RF amplifier (or called as driver) is a desktop instrument specially designed for high-speed lithium niobate electro-optic modulator. This instrument can amplify the small high-speed signal level to the higher level that can drive the modulator, thus driving the lithium niobate (LiNbO3) electro-optic modulator to work, and has good gain flatness in the broadband range.

Features:

• High bandwidth: 10, 20 or 40 GHz

• Variable gain

• The output range is up to 8V

• Highly integrated

• Easy to use

Applications:

• 10/20/40G optical modulating system

• Fiber optic testing system

• Optical fiber sensing system

Parameters of SCQ-RF-40 Driver

Limit Conditions

Eye Diagram

Ordering Information:

3.2 MZM Bias Controller

The bias controller is specially designed for Mach-Zehnder modulators to ensure a stable operation state in various operating environments. Based on its fully digitized signal processing method, the controller can provide highly stable performance. The controller injects a low frequency, low amplitude dither signal together with bias voltage into the modulator. It keeps reading the output from the modulator and determines the condition of the bias voltage and the related error. A new bias voltage will be applied afterwards according to the previous measurement. In this way, the modulator is ensured to work under proper bias voltage.

Features:

• Bias voltage control on Peak/Null/Q+/Q−

• Bias voltage control on arbitrary point

• Ultra precise control: (1) 50dB maximum extinction ratio on Null mode; (2) ±0.5◦ accuracy on Q+ and Q− modes

• Low dither amplitude: (1) 0.1% Vπ at NULL mode and PEAK mode; (2) 2% Vπ at Q+ mode and Q− mode

• High stability: with fully digital implementation

• Low profile: 40mm(W) × 30mm(D) × 10mm(H)

• Easy to use: (1) Manual operation with mini jumper; (2) Flexible OEM operations through MCU UART2

• Two different modes to provide bias voltage: (1) Automatic bias control; (2) User defined bias voltage

Application:

• LiNbO3 and other MZ modulators

• Digital NRZ, RZ

• Pulse applications

• Brillouin scattering system and other optical sensors

• CATV Transmitter

Ordering Information

Part No.: SCQ-RF-BC

Remark: (1) The highest extinction ratio depends on and cannot exceed modulator maximum extinction ratio. (2) UART operation is only available on some version of the controller.

Performance:

Maxim DC Extinction Ratio:

In this experiment, no RF signals were applied to the system. Pure DC extinction has been measured.

(1) Figure 3 demonstrates the optical power of modulator output, when modulator controlled at Peak point. It shows 3.71dBm in the diagram.

(2) Figure 4 shows the optical power of modulator output, when modulator controlled at Null point. It shows -46.73dBm in the diagram. In real experiment, the value varies around -47dBm; and -46.73 is a stable value.

(3) Therefore, the stable DC extinction ratio measured is 50.4dB.

Requirements for High Extinction Ratio:

(1) System modulator must have high extinction ratio. Characteristic of system modulator decides the maximum extinction ratio can be achieved.

(2) Polarization of modulator input light shall be taken care of. Modulators are sensitive to polarization. Proper polarization can improve extinction ratio over 10dB. In lab experiments, usually a polarization controller is needed.

(3) Proper bias controllers. In our DC extinction ratio experiment, 50.4dB extinction ratio has been achieved. While the datasheet of the modulator manufacture only lists 40dB. The reason of this improvement is that some modulators drift very fast. Our SCQ-RF-BC-ANY bias controllers update the bias voltage every 1 second to ensure fast track response.

Specifications:

1 MER refers to Modulator Extinction Ratio. The extinction ratio achieved is typically the extinction ratio of modulator specified in modulator datasheet.

2 CSO refers to composite second order. To measure CSO correctly, the linear quality of RF signal, modulators and receivers shall be

ensured. In addition, the system CSO readings may vary when running at different RF frequencies.

3 Please be noted that input optical power does not correspond to the optical power at selected bias point. It refers to the maximum optical power that the modulator can export to controller when bias voltage ranges from −Vπ to +Vπ .

1 Some MZ modulators have internal photodiodes. Controller setup should be chosen between using controller’s photodiode or using modulator’s internal photodiode. It is recommended to use controller’s photodiode for lab experiments for two reasons. Firstly, controller photodiode has ensured quality. Secondly, it is easier to adjust the input light intensity. Note: If using modulator’s internal photodiode, please make sure that the output current of photodiode is strictly proportional to input power.

2 Polar pin is used to switch the control point between Peak and Null in Null control mode(determined by Mode Select pin) or Quad+ and Quad- in Quad control mode. If jumper of polar pin is not inserted, the control point will be Null in Null mode or Quad+ in Quad mode. Amplitude of RF system will also affect the control point. When there is no RF signal or RF signal amplitude is small, controller is able to lock the work point to correct point as selected by MS and PLR jumper. When the RF signal amplitude exceeds certain threshold, polar of the system will be changed, in this case, the PLR header should be in the opposite state, i.e. the jumper should be inserted if it is not or pulled out if it is inserted.

Typical Application:

The controller is easy to use as follows:

Step1. Connect 1% port of the coupler to the photodiode of the controller.

Step2. Connect bias voltage output of the controller (through SMA or 2.54mm 2-pin header) to bias port of the modulator.

Step3. Provide controller with +15V and -15V DC voltages.

Step4. Reset the controller and it will start to work.

NOTE. Please be ensured that RF signal of the whole system is on before resetting the controller.