How ASE Light Sources Are Used in Fiber Optic Gyroscopes

An ASE light source is used in many interferometric fiber optic gyroscopes (IFOGs) because its broadband, low-coherence output can reduce sensitivity to coherent backscatter and polarization-related nonreciprocity. But “1550 nm ASE” is not a complete source specification. A usable FOG source must match the gyro architecture, coil and integrated optics, spectral bandwidth definition, polarization behavior, power at the detector, noise performance, fiber interface, and package. OmniWavelength’s current catalog includes ASE families around 1030/1064 nm, C-band, L-band, and combined C+L coverage, but the correct choice depends on the complete optical design.

What the ASE source does in a fiber optic gyroscope

An interferometric FOG uses the Sagnac effect: light is split into two waves that travel in opposite directions around a fiber coil, and rotation changes the phase relationship detected when the waves return. A simplified optical path is:

ASE source → isolator/coupler → polarizer and phase modulator/MIOC → fiber coil → detector → control electronics

The source does not measure rotation by itself. It establishes the optical conditions under which the rest of the interferometer can measure a small phase difference. Its spectrum, polarization, intensity noise, stability, and delivered power all become part of the gyro error budget.

Published designs show why there is no universal “FOG ASE specification.” A peer-reviewed 1030 nm IFOG study used a Yb-doped ASE source with approximately 15 nm optical bandwidth, while research on low-noise IFOG sources highlights relative intensity noise (RIN) as a possible limit once detector power is increased. Those are architecture-specific engineering examples, not a drop-in requirement for every gyro.

For a conventional broadband IFOG, ASE is a strong starting point. For a resonant FOG or another architecture that relies on a defined carrier, cavity interaction, or frequency control, confirm the source architecture with the gyro designer before choosing an ASE product.

Four source decisions to make before comparing products

1. Identify the gyroscope architecture

Start by stating whether the source feeds an open-loop IFOG, closed-loop IFOG, resonant FOG, or a laboratory demonstrator. The source requirement can change with the coil, coupler, polarizer, phase modulator, detector, and signal-processing method.

Include the coil fiber type, integrated optical chip, detector type, and target wavelength in the RFQ.

2. Match the wavelength to the complete optical path

1550 nm is common in telecom-band fiber systems, but it is not automatically the best wavelength for every gyro. A 1030 or 1064 nm design may use different fiber, couplers, coatings, detectors, and integrated optics. The center wavelength also affects the scale factor and the source bandwidth needed by the design.

Choose the wavelength from the coil and optical components first. Use the catalog to find a source that fits that design; do not redesign the gyro around the most convenient product page.

3. Define bandwidth before comparing numbers

“Bandwidth” is only meaningful with its definition. The current catalog uses different spectral levels for different ASE families:

• the 1030 nm family gives a 10 dB spectrum range;
• the 1064 nm family gives a 10 dB spectrum range;
• the C-band family gives a 2 dB spectrum range;
• the L-band family gives a 2.5 dB spectrum range; and
• the C+L family gives a 3 dB spectrum range.

These ranges cannot be ranked directly by their nanometer numbers. Request the spectrum at the intended output power and ask for the level, tolerance, flatness, ripple, and test temperature.

4. Separate source output from detector power

The source rating is not the same as the power reaching the photodetector. A simple first estimate is:

Pdetector = Psource × 10^(-loss_dB / 10)

For example, an illustrative 100 mW source followed by 4 dB of total optical loss would deliver about 40 mW before any additional splitter or detector limit. The actual FOG design may require far less power at the detector, so more source power is not automatically better. Excess power can worsen saturation, thermal load, or source-noise behavior.

Current ASE options and their practical trade-offs

The following comparison uses current public product-page values. They are configuration-dependent catalog examples, not guarantees that every option in a family has the same spectrum, fiber, power, or package.

Current catalog family	Public spectral and power information	Fiber and polarization options	Practical FOG question
1030 nm ASE broadband source	1030 nm center wavelength; 1018–1044 nm spectrum at the 10 dB definition with ±2 nm tolerance; 10–1000 mW options; 10–100% adjustment on tunable versions	Hi-1060 SM or PM980 fiber; PM configurations are listed from 10 to 100 mW; FC/APC	Is the coil, MIOC, detector, and gain medium designed for the 1 µm band, and is the requested PM power available?
1064 nm ASE broadband source	1064 nm center wavelength; the page lists 1040–1080 nm or 1030–1080 nm 10 dB ranges depending on configuration; 10–1000 mW options; ±2 nm tolerance	Hi-1060 SM or PM980 fiber; PM configurations are listed from 10 to 100 mW; FC/APC	Which spectrum range applies to the quoted configuration, and does it match the gyro’s detector and coil response?
C-band ASE broadband source	1528–1569 nm at the 2 dB definition with ±0.5 nm tolerance; SM 10–500 mW; PM 10–200 mW; PSD listed from −6 to +11 dBm/nm; flatness ≤2 dB at 10–200 mW, ≤3 dB at 300–500 mW, and ≤1 dB for the F1 option	G652D/SMF-28 SM or PM1550 PM; the page lists completely unpolarized SM output and linear PM output; FC/APC	Is C-band coverage enough, and is the gyro optimized for a low-polarization or a polarization-defined source?
L-band ASE broadband source	1567–1603 nm at the 2.5 dB definition; 10–200 mW; flatness ≤2.5 dB typical and ≤3 dB maximum; PSD is listed from −6 dBm/nm at 10 mW to +7 dBm/nm at 200 mW	SMF-28 SM or PM1550 PM; completely unpolarized SM and linear PM options; FC/APC	Does the coil, filter, detector, and downstream optics actually use the L-band rather than the C-band?
C+L band ASE broadband source	1528–1603 nm at the 3 dB definition with ±0.5 nm tolerance; 10–200 mW; flatness ≤3 dB up to 100 mW and ≤6 dB at 200 mW	SMF-28 SM or PM1550 PM; FC/APC; M15/M20 module or B1 benchtop package	Does one gyro bench need both bands badly enough to accept the broader source’s configuration-specific flatness trade-off?

The useful comparison is the spectrum delivered at the power, polarization, and reference plane used by the gyro—not the largest nanometer headline.

How to choose a source by FOG use case

A 1550 nm IFOG with a defined C-band optical path

Start with the C-band source when the coil, couplers, filters, and detector are designed for 1550 nm and the required spectrum fits 1528–1569 nm. Its public page offers a wider SM power range than its PM range, and the flatness changes with output-power class. That makes the 10–200 mW, 300–500 mW, and F1 options different engineering choices rather than interchangeable power settings.

Choose the L-band source only when the optical path is deliberately designed for 1567–1603 nm. It is not a simple “higher wavelength” version of the C-band source: its spectrum definition, power ceiling, PSD values, and flatness figures are different.

A dual-band or wide-spectrum laboratory setup

The C+L source is useful when one bench must cover both telecom windows or when the gyro experiment needs a wider combined spectrum. The trade-off is visible in the current specifications: the page lists ≤3 dB flatness for configurations up to 100 mW and ≤6 dB at 200 mW. If the measurement depends on a uniform spectrum, compare that flatness with the actual system requirement before choosing the 200 mW option.

Wider coverage does not automatically improve gyro performance. The coil, integrated optics, detector, and signal processing must support the full band; a narrower matching source can be more predictable.

A 1030 or 1064 nm IFOG

Use the 1030 or 1064 nm families when the gyro has been designed around the 1 µm band. The current pages provide higher listed power options than the telecom-band ASE families, but the PM options are narrower than the total SM power range. The exact 10 dB spectrum range also varies by configuration on the 1064 nm page.

This is where a published 1030 nm IFOG example is useful as context: a research system used Yb-doped ASE around 1030 nm and characterized its optical bandwidth and detector power as part of the gyro design. It does not mean every 1030 nm source or every 1030 nm gyro should use the same bandwidth or power.

A lab prototype versus an embedded instrument

Benchtop and module formats answer different integration problems. A B1 or B2 benchtop unit is easier to adjust and observe during a prototype experiment. An M15, M20, M27, or M31 module is more suitable when the source must live inside an instrument, but the RFQ must include the DC supply, thermal path, mounting, control interface, fiber exit, and service access.

The current ASE pages commonly list touchscreen and RS232 control for benchtop versions and RS232 control for modules. Confirm the command set and startup behavior before integration.

The specifications that most often decide FOG performance

RIN is an RFQ item, not a conclusion from “broadband”

Broadband ASE can reduce unwanted coherent effects, but broadband output alone does not guarantee low gyro noise. The public OmniWavelength ASE pages reviewed for this article list spectrum, PSD, flatness, stability, polarization, isolation, fiber, and package information, but they do not publish a complete RIN spectrum for every configuration.

Ask for RIN or excess-noise data at the intended power, detector bandwidth, and measurement conditions. If the supplier cannot provide a directly comparable RIN result, keep source noise as an acceptance test rather than assuming the largest power option is the best one.

Flatness and ripple need the same reference conditions

A flatness value must be tied to a power setting and spectral definition. For example, the current C-band page separates ≤2 dB flatness for 10–200 mW from ≤3 dB for 300–500 mW and identifies a ≤1 dB F1 option. The C+L page separately lists ≤3 dB up to 100 mW and ≤6 dB at 200 mW.

Ask for the actual spectrum at the quoted configuration. If the gyro algorithm or calibration assumes a particular spectral shape, request the data file or an acceptance plot instead of relying on a headline bandwidth.

Polarization must match the coil and integrated optics

Do not treat SM and PM as a simple good/better ranking. Standard SM output can be suitable when the source should be unpolarized or when the downstream polarizer/MIOC defines the operating polarization. PM output can be important when the coil and optical path are polarization-maintaining and the system needs a defined axis.

The current C-band and L-band pages describe SM output as completely unpolarized and PM output as linear, with PER values shown for the respective configurations. DOP and PER are not interchangeable labels. Ask for the measurement definition, guaranteed value, connector key orientation, and behavior across temperature and output power.

Stability is only useful with its time window

The current C-band and L-band pages list short-term stability of ≤±0.02 dB over 15 minutes and long-term stability of ≤±0.05 dB over 8 hours. Those values are useful starting points, but a gyro RFQ should also state warm-up time, temperature, power setting, measurement reference plane, and whether the result is maximum deviation, peak-to-peak, or another definition.

Questions to put in the RFQ

Send the supplier the following information before asking for a model number:

1. Gyro architecture: Is this an open-loop IFOG, closed-loop IFOG, resonant FOG, or another design? Include the coil type, integrated optics, detector, and modulation method.
2. Wavelength target: What center wavelength and usable spectrum does the coil and detector require? State whether the band is defined at 2 dB, 3 dB, 10 dB, FWHM, or another level.
3. Spectral shape: What flatness, ripple, minimum PSD, center-wavelength tolerance, and temperature drift are acceptable at the requested output power?
4. Power budget: What power is required at the detector and at the coil input after splitter, coupler, connector, and fiber losses? What detector saturation or thermal limit must not be exceeded?
5. Noise: Provide the required RIN or excess-noise limit, measurement bandwidth, and test condition. Ask whether the quoted data are typical or guaranteed.
6. Polarization and fiber: Do you need unpolarized SM output or linear PM output? Confirm fiber type, connector, key orientation, pigtail length, isolation, and reflection sensitivity.
7. Integration: Choose benchtop or module format, then confirm dimensions, heat path, supply, RS232 command set, interlock, startup time, fault reporting, and environmental limits.
8. Acceptance data: Request the spectrum, power, stability, polarization, and noise measurements for the exact configuration being shipped.

For background on how ASE differs from another low-coherence option, see the existing ASE vs SLD broadband-source comparison. It is useful when the gyro team is still deciding between source architectures, but it does not replace an FOG-specific noise and integration review.

Conclusion

ASE is a practical source class for many interferometric fiber optic gyroscopes because it can provide broadband, low-coherence optical power in a fiber-delivered format. The buying decision still has to be made at system level. Match the source to the gyro architecture, wavelength, bandwidth definition, spectral shape, detector power, RIN, polarization, fiber, connector, package, and control interface.

If you need a matched configuration, contact OmniWavelength engineering sales with the coil wavelength, required spectrum, detector power, polarization, fiber/connector, package, and control details.

Frequently asked questions

Is an ASE source only used in interferometric fiber optic gyroscopes?

No. ASE is a strong starting point for many broadband IFOG designs, but resonant FOGs and other architectures can require different source behavior. Confirm the optical architecture before selecting a source.

Should I choose 1030/1064 nm or 1550 nm for a FOG?

Choose the wavelength that matches the coil, integrated optics, detector, fiber, and system calibration. The current catalog supports both 1 µm-class and telecom-band ASE families, but their spectrum definitions, power ranges, and PM options are different.

How much ASE output power does a fiber optic gyroscope need?

There is no universal number. Calculate the required detector and coil power after optical losses, then check detector saturation, thermal limits, and source noise. Ask for power at the correct reference plane instead of sizing from the source headline rating.

Do I need PM fiber for an ASE-based FOG?

Only when the coil and downstream optical path require a defined polarization state. A PM output is not automatically better, and it is not the same as a low-DOP unpolarized output. Confirm the MIOC, polarizer, coil, PER, axis orientation, and connector requirements together.

Is a C+L ASE source better than a C-band or L-band source?

Not automatically. C+L is useful when one setup genuinely needs both bands, but the broader range introduces its own flatness, PSD, detector, and calibration questions. Compare the full spectrum at the intended output power before choosing it.