Optical Communication

 

Advantages of Using Infini-LightTM Broad-Band Light Source:

We provide the most cost-effect and highest performance optical fiber broad-band light sources for the telecomm and datacomm industry for manufacturing, testing, and qualifying fiber optics products (such as WDM, splitter, isolator, circulator, and optical switch, etc.) that require spectral measurement across a broad wavelength range. In order to meet the stringent industrial standards, Infinon Research uses several proprietary electrical and optical elements to construct the Infini-LightTM broad-band source and deliver unprecedented performance compared to products offered by other industrial leaders. The following sections describe in details the advantages of using this broad-band light source as compared to other type of equipments.

 

Best Technology
There are several different technologies to deliver broad-band light into a single-mode fiber. The first one is using tungsten-halogen filament to create a white-light radiation and couple into a single-mode fiber with a high power lens. This type of source provides a true broad-band light (from UV to IR) with relatively flat spectrum. However, due to the energy density limitation that can be created by the filament, typically the power that can be collected by the single-mode fiber is about -55dBm/nm in the 1550nm IR range, which is too small to support high dynamic range measurement for DWDM components using common optical spectrum analyzers (OSA). The second technology is light-emitting-diode (LED), which can deliver -15dBm of total energy into a single-mode fiber. It has a Gaussian-shape spectrum, typically with ~50nm of half-maximum width. This means that the optical power at wavelength peak is about -35dBm/nm, and decreases toward the side-bands. Although its optical density is ~100 times larger than the filament white-light source, the energy level at its side-bands is still too low for today’s DWDM testing systems. The third one is amplified-spontaneous-emission (ASE) source from rare-earth ion doped fiber which is optically pumped at another wavelength and radiates the broadband light when the rare-earth ions relax from their excited state to a lower energy state. This source can deliver high optical density (>-20dBm/nm) within the ion emission spectral window if pumped with high energy. However, the spectral width is comparably small (<50nm wide), and one needs different ion-doped fiber to cover different wavelength ranges.
The last, and best, technology as used by the Infini-Light is semiconductor super luminescent diode (SLD). SLD is similar to an LED source, but can put out >30 times more optical power into the single-mode fiber. The output wavelength range is defined by the composition of semiconductor materials and can be easily tailored to any desired wavelength in the communication window.

 

Ultra Broad Band
The Infini-Light, with all its wavelength options installed, can deliver usable wavelength from 1270nm to 1650nm from one single fiber output. It eliminates the need of combining several different ASE light sources at different wavelength bands externally, reducing the complexity on the manufacturing floor. It also maintains the high optical power of each individual SLD with our proprietary combining technique. Currently, if one wants to use ASE fiber sources to cover a broad wavelength window, he/she needs to use a C/L-band Er ASE source to cover 1530nm to 1610nm, an S-band Th ASE source to cover 1440nm to 1500nm, and an O-band Pr ASE source to cover 1270nm to 1325nm, and there are still “blind spots” between the wavelength windows, like 1325nm to 1440nm, that are still missing. Although Infini-Light has less total optical power than common ASE sources, it can deliver more than -33dBm/nm of minimum optical power density within the entire specified wavelength window. And the power density at wavelength peak of each SLD can reach more than -20dBm/nm. This feature provides an “all-in-one”Light source for testing any WDM components, such as C/L-band DWDM, S- and O-band pump laser combiner and fiber grating, 1310/1550nm WDM, and most importantly the emerging CWDM for metro networks that runs from 1270nm to 1610nm with 20nm of channel spacing. This greatly saves the equipment cost for component/system manufacturers who want to use the same testing setup and switch to different components frequently.

 

Ultra High Power
The Infini-Light uses industrial-leading super luminescent semiconductor diode (SLD) to cover a broad wavelength range with high optical power as mentioned in the previous section. Compared to similar product using conventional LED technology which provides only about -35dBm/nm at the wavelength peaks, the Infini-Light is almost 30 times brighter, which means that it can be split to 30 testing stations and provide the same power density as the conventional LED sources. It also means that Infini-Light can support higher measurement sensitivity during the testing (>40dB of dynamic range with 0.1nm of typical resolution bandwidth) for standard DWDM components. With its high power, it is even possible to make a continuous scanning narrow-band source using a tunable band-pass filter and split the light to multiple-stations, just like a tunable laser but covering a much broader range (>350nm compared to 50nm for a tunable laser). Therefore, one can use a power meter to measure the component spectrum and replace the costly optical spectrum analyzer on every station.

 

Low Degree of Polarization
Although an ASE source can provide broad band light with very low degree of polarization (DOP)[1] <#_ftn1> due to its random nature of the atomic photon emission, the complexity and high cost has put limits on their applications for very broad bandwidth as mentioned before. If one uses SLD or LED as the light source, the polarization state of the output light becomes significant (normally more than 40% for LED and more than 70% for SLD) because of the quantum-well structure of the semiconductor waveguide. Infini-Light uses a proprietary optical power processing technique to eliminate the degree of polarization of the output light from the SLD, achieving typical DOP of less than 10%. This feature is very important for components with high polarization dependent loss (PDL) or wavelength (PDλ), and for power meters or OSAs with high polarization-dependent sensitivity. Therefore, Infini-Light can provide repeatable testing results for each device. In addition, its polarization reduction process is carefully designed so that one can use spectral resolution bandwidth as small as 0.01nm without any power instability or ripple in the spectrum to ensure the testing accuracy. This low DOP feature is a significant difference from other competing products.

 

External Modulation
In research labs sometimes it is desirable to modulate the light source directly and use it with a lock-in amplifier for ultra-high sensitivity optical signal measurement which could be influenced by the room light on a bench-top setup. The ASE sources can not be directly modulated to above 300 Hz due to the long spontaneous emission life time of the atomic elements. Therefore, most ASE sources are not equipped with external modulation capability. The Infini-Light uses semiconductor SLD sources which can be easily modulated by external TTL signals to 2 MHz, sufficient for most lock-in amplifiers and other applications, such as data communications. Higher modulation speed (up to 200 MHz) is possible by using more advanced driving circuits as an upgraded version of this product.

 

Excellent Optical Power Stability
The Infini-Light uses industrial-leading electronic circuits, enclosure design, and thermal management to ensure the power stability of the output light. When maintained at constant room temperature, the output power variation is typically less than 0.02dB within the entire spectral window during one hour of usage. This reduces the need of regular power reference when testing large number of similar devices. In addition, during a dynamic testing environment that needs constant fiber cleaving and splicing, the Infini-Light also incorporates optical isolators to reject external optical reflection from the cleaved fiber ends to eliminate the power instability during testing.

 

Low Cost
As mentioned in the previous sections, one needs to use several different ASE sources to barely achieve coverage from 1270nm to 1610nm and still missing some wavelength bands. In comparison, Infini-Light combines several low cost SLD’s to deliver a truly continuous broad-band optical power in a single unit. This results in a cost reduction of more than 60% from the ASE source approach, and minimizes the maintenance cost of the testing setup. This is the most important advantage for today’s capital-spending sensitive telecomm industry.

 

Conclusion
In summary, the Infini-Light provides the advantages of high power, broad-band, simplicity, high stability, low polarization dependency, and most importantly, low cost for today’s advanced optical fiber component and system manufacturers that gradually migrate to utilize the whole communication windows (O, E, S, C, and L bands from 1270nm to 1650nm). Therefore, the Infini-LightTM will be the only choice of broad-band light source for anyone who wants to maintain a competitive position in the future fiber optics industry.

 

Applications:
●Material Absorption Spectroscopy.
●WDM Components Testing.
●Telecomm and Datacomm Systems.
●Optical Coherence Tomography.
●Optical Fiber Sensors.

 

DM:
Broadband Fiber-Optic Light Source
Near-Infrared Broadband Fiber-Optic Light Source