Ultra Compact IQ Modulator Bias Controller Automatic Bias Controller

Short Description:

Rofea’ modulator 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 ultra 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 afterwords according to the previous measurement. In this way, the modulator is ensured to work under proper bias voltage.

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Product Detail

Rofea Optoelectronics offer Optical and photonics Electro-optic modulators products

Product Tags

Feature

•Provides three biases for IQ modulators Modulation format independent:
•QPSK, QAM, OFDM, SSB verified
•Plug and Play:
No manual calibration needed Everything automatic
•I, Q arms: controll on Peak and Null modes High extinction ratio: 50dB max1
•P arm: controll on Q+ and Q- modes Accuracy: ± 2◦
•Low profile: 40mm(W) × 28mm(D) × 8mm(H)
•High stability: fully digital implementation Easy to use:
•Manual operation with mini jumper Flexible OEM operations through UART2
•Two modes to provide bias voltages: a.Automatic Bias Control b.User defined bias voltage

Electro-optic modulator Electro-optical modulator Modulator Bias Controller Bias point controller IQ Modulator DP-IQ Modulator Automatic Bias Controller

Application

•LiNbO3 and other IQmodulators
•QPSK, QAM, OFDM, SSB and etc
•Coherent Transmission

Performance

Figure 1. Constellation (without controller)

Figure 2. QPSK Constellation(with controller

Figure 3. QPSK-Eye pattern

Figure 5. 16-QAM Constellation pattern

Figure 4. QPSK Spectrum

Figure 6. 16-QAM Spectrum

Specifications

Parameter	Min	Typ	Max	Unit
Controll Performance
I, Q arms are controlled on Null(Minimum) or Peak(Maximum) point
Extinction ratio		MER¹	50	dB
P arm is controlled on Q+(right quadrature) or Q-( left quadrature) point
Accuracy at Quad	−2		+2	degree²
Stablization time	15	20	25	s
Electrical
Positive power voltage	+14.5	+15	+15.5	V
Positive power current	20		30	mA
Negative power voltage	-15.5	-15	-14.5	V
Negative power current	8		15	mA
Output voltage range	-14.5		+14.5	V
Dither amplitude		1%Vπ		V
Optical
Input optical power³	-30		-8	dBm
Input wavelength	1100		1650	nm

1. MER refers to Modulator Extinction Ratio. The extinction ratio achieved is typically the extinction ratio of modulator specified in modulator datasheet.
2. 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 .

User Interface

Figure5. Assembly

Group	Operation	Explanation
Reset	Insert jumper and pull out after 1 second	Reset the controller
Power	Power source for bias controller	V- connects the negative electrode of the power supply
		V+ connects the positive electrode of the power supply
		Middle port connects with the ground electrode
Polar¹	PLRI: Insert or pull out the jumper	no jumper: Null mode; with jumper: Peak mode
	PLRQ: Insert or pull out the jumper	no jumper: Null mode; with jumper: Peak mode
	PLRP: Insert or pull out the jumper	no jumper: Q+ mode; with jumper: Q- mode
LED	Constantly on	Working under stable state
	On-off or off-on every 0.2s	Processing data and searching for controlling point
	On-off or off-on every 1s	Input optical power is too weak
	On-off or off-on every 3s	Input optical power is too strong
PD ²	Connect with the photodiode	PD port connects the Cathode of the photodiode
PD ²	Connect with the photodiode	GND port connects the Anode of the photodiode
Bias Voltages	In, Ip: Bias voltage for I arm	Ip: Positive side; In: Negative side or ground
	Qn, Qp: Bias voltage for Q arm	Qp: Positive side; Qn: Negative side or ground
	Pn, Pp: Bias voltage for P arm	Pp: Positive side; Pn: Negative side or ground
UART	Operate controller via UART	3.3: 3.3V reference voltage
		GND: Ground
		RX: Receive of controller
		TX: Transmit of controller

1 Polar depends on system RF signal. When there is no RF signal in the system, the polar should be positive. When RF signal has amplitude greater than a certain level, the polar will change from positive into negative. At this time, Null point and Peak point will switch with each other.Q+ point and Q- point will switch with each other as well.Polar switch enables user to change the polar

directly without changing operation points.

² Only one choice shall be chosen between using controller photodiode or using modulator photodiode. It is recommended to use controller photodiode for Lab experiments for two reasons. Firstly, controller photodiode has ensured qualities. Secondly, it is easier to adjust the input light intensity.If using modulator’s internal photodiode, please make sure that the output current of photodiode is strictly proportional to input power.

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Rofea Optoelectronics offers a product line of commercial Electro-optic modulators, Phase modulators, Intensity modulator, Photodetectors, Laser light sources, DFB lasers,Optical amplifiers, EDFA, SLD laser, QPSK modulation, Pulse laser, Light detector, Balanced photodetector, Laser driver, Fiber optic amplifier, Optical power meter, Broadband laser, Tunable laser, Optical detector, Laser diode driver, Fiber amplifier. We also provide many particular modulators for customization, such as 1*4 array phase modulators, ultra-low Vpi, and ultra-high extinction ratio modulators, primarily used in universities and institutes.
Hope our products will be helpful to you and your research.

Automatic Bias Control Module