Newport 2101 High-Dynamic-Range Power Sensors User Guide

Newport 2101 High-Dynamic-Range Power Sensors

CAUTION

These power sensors are sensitive to electrostatic discharges and could be permanently damaged if subjected even to small discharges. Ground your-self adequately prior to handling these detectors or making connections. A ground strap provides the most effective grounding and minimizes the likelihood of electrostatic damage

Warranty

Newport Corporation guarantees its products to be free of defects for one year from the date of shipment. This is in lieu of all other guarantees, expressed or implied, and does not cover incidental or consequential loss. Information in this document is subject to change without notice. Copyright 2022, Newport Corporation. All rights reserved. The New Focus logo and symbol are registered trademarks of Newport Corporation Document Number 90099910 Rev. A

Operation

Introduction

Models 2101 and 2103 High-Dynamic-Range Power Sensors are sensitive optical receivers with logarithmic conversion circuitry to provide an analog output spanning a range of more than 70 dB of optical input power. Designed for use in swept-wavelength optical loss measurement, the fast rise and fall times allow measurements at speeds of 100 nm/s and beyond. For Model 2103, the provided calibration data enables accurate absolute power measurement over the wave-length range from 1520 nm to 1620 nm. Outside of the calibrated band, both the Model 2101 and Model 2103 work well as relative power sensors. The logarithmic output provides a conversion gain of 50 mV/dB of optical power, so the full range of the sen-sor can be converted to a digital signal with better than 0.01-dB resolution using a single 14-bit, 5-V conversion. This simplifies data collection, eliminating the need for user-controlled gain switch-ing and multiple-laser sweeps. As a result, data can be taken more quickly and without the added accuracy concerns that result from stitching errors between multiple sweeps. The fast analog response is also useful for viewing high-range signals on an oscilloscope, making the Model 2101 and 2103 good tools for general lab use. Multiple units can be bolted together and their power

Basic Operating Information

1. Multiple units may be bolted together using screws found in threaded storage holes in the bottom of the unit. Power connections can be daisy-chained from one unit to the next using the short cables provided.
2. The Model 2101 accepts free space light input; FC/PC and FC/APC fiber inputs are available with the Model 1281 fiber adapter accessory. The Model 2103 accepts both FC/PC and FC/APC input connectors.
3. A ±15-V, 75-mA power supply is required. In daisy-chained applications with N power sensors, the power supply should be rated for N times 75 mA.
4. The output is an analog voltage with a gain of 50 mV/dB of input light. For the Model 2101, a 3.5-V output typically corresponds to approximately 2 dBm of input optical power at 920 nm. A 3.5-V output corresponds to approximately 0 dBm of input power at 1550 nm for the Model 2103.
5. For the Model 2103, calibration information for precise measurements in the 1520-nm to 1620-nm range are provided on a sheet of paper found in the back of the manual.

Details of Operation

Optical Input
The Model 2101 accepts both free space and FC fiber input. A 5-mm diameter photodiode makes the free space light easy to align. The Model 2103 accepts both FC/PC and FC/APC input connectors. The fiber illuminates a 1-mm photodiode at sufficiently close range so that all the light is detected from both fiber types. The fiber is perpendic-ular to the diode so that the non-angle-polished input fibers result in the specified polarization dependence of <0.02 dB. The typical wavelength dependence of the response is shown in Figure 1 for Model 2101 and Figure 2 for Model 2103, respectively. The vertical axis is in optical dB, and the horizontal axis is in optical wavelength µm.

Figure 1: Wavelength response of Model 2101 vs. wavelength.

Figure 2: Wavelength response of Model 2103 vs. wavelength.

Calibration Data (Model 2103 Only)

To correct for wavelength response of the photodiode, calibration information is provided on a sheet of paper found in the back of the manual. These are the offsets (in volts) which must be subtracted from measured values in order for a 0-dBm input to produce 0 V at the output. Input optical power is then given by P(dBm) = 20 x (Vmeas – Vcal)

Warm-up Time

Active temperature stabilization of the photodiode and critical circuit components requires a warm-up time of about five minutes for full accuracy. Within this period, the status light (for Model 2103) changes from red to green and the output varies by several dB as the temperature stabilizes. Failure of the status light to turn green indicates the ambient temperature is outside the operating range, and Model 2103 may not give accurate readings. Model 2101 has no status light.

Output Signal

The output of the Models 2101 and 2103 is an analog voltage with a gain of 50 mV per dB of input light. For Model 2101, a 3.5-V output corresponds to approximately 2 dBm of input power at 920 nm; the accuracy degrades for signals outside the specified range of 0.4 V to 3.7 V (-60 dBm to +6 dBm). For the Model 2103, a 3.5-V output corresponds to approximately 0 dBm of input power at 1550 nm. While the output range is about -0.2 V to 3.75 V (-74 dBm to +5 dBm), accuracy degrades for signals outside the specified range of 0.4 V to 3.7 V (-62 dBm to +4 dBm). The unit must be connected to a high-impedance load; it cannot drive a 50-ohm load.

Measurement Speed

The Models 2101 and 2103 have three filter settings (1, 5, and 25 kHz) to reduce noise when speed of response is not critical. The fastest setting results in a 0-100% small signal rise time of 30 µs and an analog bandwidth in excess of 25 kHz. At this speed, the Models 2101 and 2103 can be used to measure narrow optical filters at wavelength sweep speeds of 100 nm/s.
To determine whether a slower filter setting can be used for swept-wavelength measurements, compare a measurement of the device under test at a faster sweep speed to one at a slower sweep speed (e.g., four times slower). If the faster measurement does not distort the result, the filter can be used.

Cross-over Detail

The Models 2101 and 2103 employ fast switching to achieve essentially seamless range-changing between two gain levels. This feature results in slight discontinuities (of both signal and noise) at the crossover point near the output level of -29 dBm for Model 2101 and 1.95 V (-31 dBm) for Model 2103. Figure 3 shows an example of the crossover. This will be insignificant for most applications but should be kept in mind.

Figure 3: Close-up detail of crossover point for a sine-wave input

Noise Levels

The electrical noise voltage present at the output divided by the gain (50 mV/dB) of the power sensor represents the noise referred to the input. A plot of this is shown in Figure 4 for the 25-kHz filter setting. Note the discontinuity at the crossover.

Figure 4: Typical noise of the Model 2103 versus signal level

Multi-Channel Testing

Ganging Multiple Units
Multiple units can be bolted together to help maintain an orderly benchtop or to mount in a rack. Screws for this are located in storage holes in the bottom of the unit; these screws fit in the mating tabs (see Figure 5). When bolted together, the short power cables provided with each unit are used to daisy chain the power connections so a single supply can power multiple units. The Newport Model 0901 15-V Power Supply can power a total of nine units (four from each of the two 300-mA outputs, and one from the 100-mA output.)

Figure 5: Ganging of Model 2103, front view. Daisy-chained power cables not shown.

Physical Specifications

Figure 6: Front, side and back views of the Model 2101

Figure 7: Front, side and back views of the Model 2103

Figure 8: Single unit configuration

Characteristics

optimized at 1550 nm
Bandwidth Settings (3 dB)| 1, 5, 25 kHz| 1, 5, 25 kHz
Transition Time 0–100%, 25 kHz setting| 30 µs| 30 µs
Maximum Power*| 6 dBm

(920 nm typical)

| 4 dBm
rms Noise Floor*| -69 dBm

(920 nm typical)

| -71 dBm
Calibrated Accuracy (0 dBm, 22˚ C)| n/a| 0.1 dB
Relative Accuracy (-61 to +4 dBm)| 0.05 dB +63 pW (920 nm typical)| 0.05 dB + 40 pW
Optical Return Loss, Single-Mode APC| n/a| -50 dB
Polarization Dependence (FC/PC)| n/a| 0.02 dB
Repeatability| n/a| 0.01 dB
Crossover Level| -29 dBm typical| -31 dBm typical
Crossover Transient| 0.001 dB·ms| 0.001 dB·ms
Specification| Model 2101| Model 2103
---|---|---
Crossover Discontinuity| 0.03 dB| 0.03 dB
Temperature Drift| 0.005 dB/˚ C typical| 0.005 dB/˚ C typical
Output Type| Analog| Analog
Output Impedance| <1 W typical| <1 W typical
Output Reference Level* (23˚ C)| 2 dBm = 3.5 V

(920 nm typical)

| 0 dBm = 3.5 ±0.005 V
Output Slope| 0.5 V/decade| 0.5 V/decade
Output Range| -0.2 to +3.75 V typ.| -0.2 to +3.75 V typ.
Input Connector| Free space plus fiber adapter option| FC/PC or FC/APC
Power Consumption| ±15 V, 75 mA| ±15 V, 75 mA
Operating Temperature Range| 15–35˚ C| 15–35˚ C

Technical Support

Information and advice about the operation of any Newport product is availabe from our applications engineers. For quickest response, ask for “Technical Support” and know the model number and serial number for your product.
Hours: 8:00–5:00 PST, Monday through Friday (excluding holidays).
Phone: 1-877-835-9620
Support is also available by email and chat
Chat: Connect with us at www.newport.com
Email: [email protected]
We typically respond to emails within one business day.

Service

In the event that your device malfunctions or becomes damaged, please contact Newport for a return merchant authorization (RMA) number and instructions on shipping the unit back for evaluation and repair.

References

• Newport - Photonics Solutions for Extending the Frontiers of Science

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