| 1. |
- Gustavsson, Johan, 1974, et al.
(författare)
-
High-speed 850-nm VCSELs for 40 Gb/s transmission
- 2010
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have explored the possibility to extend the data transmission rate for standard 850-nm GaAs-based VCSELs beyond the 10 Gbit/s limit of today's commercially available directly-modulated devices. By sophisticated tailoring of the design for high-speed performance we demonstrate that 10 Gb/s is far from the upper limit. For example, the thermal conductivity of the bottom mirror is improved by the use of binary compounds, and the electrical parasitics are kept at a minimum by incorporating a large diameter double layered oxide aperture in the design. We also show that the intrinsic high speed performance is significantly improved by replacing the traditional GaAs QWs with strained InGaAs QWs in the active region. The best overall performance is achieved for a device with a 9 μm diameter oxide aperture, having in a threshold current of 0.6 mA, a maximum output power of 9 mW, a thermal resistance of 1.9 °C/mW, and a differential resistance of 80 Ω. The measured 3dB bandwidth exceeds 20 GHz, and we experimentally demonstrate that the device is capable of error-free transmission (BER
|
|
| 2. |
- Haglund, Erik, 1985, et al.
(författare)
-
850 nm datacom VCSELs for higher-speed and longer-reach transmission
- 2013
-
Ingår i: European VCSEL Day 2013.
-
Konferensbidrag (refereegranskat)abstract
- The 850 nm GaAs-based VCSEL is already the dominating technology for transmitters in optical interconnects up to 100 m in datacenters, thanks to low-cost fabrication, excellent high-speed properties at low currents and the existence of high-speed OM4 multimode fiber optimized for this particular wavelength. Future datacenters will require faster and more energy-efficient VCSELs to increase the overall bandwidth and reduce the power consumption of the datacenter network. In addition, longer-reach interconnects exceeding 1 km will also be required as datacenters grow into large multi-building complexes.By optimizing the doping profiles of the DBRs to reduce resistance, using a short (½-λ) cavity to improve longitudinal optical confinement and optimizing the photon lifetime for optimal damping, we obtained a record-high small-signal modulation bandwidth of 28 GHz for a ~4 µm oxide aperture VCSEL. A 7 µm oxide aperture VCSEL (~27 GHz bandwidth) enabled error-free transmission (bit-error-rate 300 m), the large spectral width of VCSELs leads to severe signal degradation by fiber dispersion. We have investigated two methods of fabricating low-spectral width quasi-single mode VCSELs to mitigate this problem. By using a small oxide aperture of ~3 µm, error-free transmission was achieved at 22 Gbit/s over 1.1 km of OM4 fiber. An alternative approach is to use an integrated mode filter in the form of a shallow surface relief to reduce the spectral width of the VCSEL. The mode filter allows for the use of a larger oxide aperture and thereby enables a lower resistance and operation at a lower current density. A 5 µm oxide aperture VCSEL with a mode filter enabled error-free transmission at 25 Gbit/s over 500 m of OM4 fiber.
|
|
| 3. |
- Haglund, Erik, 1985, et al.
(författare)
-
High-speed lasers for optical interconnects
- 2012
-
Ingår i: Swedish Optics and Photonics Days 2012.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the era of cloud computing, with services such as video streaming, social networking, and online storage and file sharing, the demand for online data processing and storage capacity is growing rapidly. These services are hosted in huge data centers that need not only fast servers but also fast communication between servers. Because copper cables have high attenuation at high frequencies, the most promising solution is to use fiber optical links (called optical interconnects) to connect different parts of the data center. Today, gallium arsenide-based vertical-cavity surface-emitting lasers (VCSELs) emitting at 850 nm are the standard light source in transmitters used in commercially available optical interconnects, operating at up to 14 Gbit/s with a link length of up to 300 m. These lasers have the advantages of low power consumption, fast direct modulation at low currents, and low-cost manufacturing. To keep up with the demand of increasing optical interconnect capacity, the Photonics Laboratory at Chalmers university of Technology is conducting research into improving the speed, reach and capacity of VCSELs for optical interconnects.
|
|
| 4. |
- Larsson, Anders, 1957, et al.
(författare)
-
High speed VCSELs for optical interconnects
- 2012
-
Ingår i: Conference Proceedings - International Conference on Indium Phosphide and Related Materials. - 1092-8669. - 9781467317252 ; , s. 269-272
-
Konferensbidrag (refereegranskat)abstract
- This paper presents an overview of our recent work on high speed, oxide confined, 850 nm vertical cavity surface emitting lasers (VCSELs). With proper active region and cavity designs, and techniques for reducing capacitance and thermal impedance, we have reached a modulation bandwidth of 23 GHz and demonstrated 40 Gbps transmission. Using an integrated mode filter for reducing the spectral width we have extended the reach on multimode fiber at 25 Gbps from 100 to 500 m. Improved link capacity was also demonstrated using a more spectrally efficient multi-level modulation format (4-PAM). Finally, a MEMS-technology for wafer scale integration of tunable high speed VCSELs was developed, enabling a tuning range of 24 nm, a 6 GHz modulation bandwidth, and 5 Gbps transmission.
|
|
| 5. |
- Szczerba, Krzysztof, 1985, et al.
(författare)
-
30 Gbps 4-PAM transmission over 200m of MMF using an 850 nm VCSEL
- 2011
-
Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:26, s. B203-B208
-
Tidskriftsartikel (refereegranskat)abstract
- We present high speed real time, error free 4-PAMtransmissionfor short range optical links based on a VCSEL operating at 850 nm, a multimode fibre and a simple intensity detector. Transmission speeds of 25 Gbps and 30 Gbps are demonstrated, and the maximum fibre reaches were 300 m and 200 m, respectively. The 4-PAM is also compared with OOK transmission at 25 Gbps, and we find that at this bit rate 4-PAM increases the error free transmission distance in the multimode fibre by 100 m, compared to OOK.
|
|
| 6. |
- Szczerba, Krzysztof, 1985, et al.
(författare)
-
30 Gbps 4-PAM transmission over 200m of MMF using an 850 nm VCSEL
- 2011
-
Ingår i: European Conference and Exposition on Optical Communications, ECOC. - 2162-2701. - 9781557529312 ; , s. 1-3
-
Konferensbidrag (refereegranskat)abstract
- Real time, error free 4-PAM transmission at 25 Gbps and 30 Gbps over 300 m and200m of multimode fiber, respectively, using a VCSEL operating at the wavelength of 850 nm.
|
|
| 7. |
|
|
| 8. |
- Szczerba, Krzysztof, 1985, et al.
(författare)
-
4-PAM for high-speed short-range optical communications
- 2012
-
Ingår i: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 4:11, s. 885-894
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we compare 4-pulse amplitudemodulation and on–off keying modulation formats at highspeed for short-range optical communication systems. Thetransmission system comprised a directly modulated verticalcavitysurface-emitting laser operating at a wavelength of850 nm, an OM3Å multimode fiber link, and a photodetectordetecting the intensity at the receiver end. The modulationformats were compared both at the same bit-rate and at thesame symbol rate. The maximum bit-rate used was 25 Gbps.Propagation distances up to 600 m were investigated at12.5 Gbps. All measurements were done in real time andwithout any equalization.
|
|
