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NRZ-encoded Signals, Manchester-encoded Signals

The industry's first NRZ and Manchester configurable protocol decoders accept a broad range of physical characteristics for NRZ- or Manchester-encoded signals.

Low differential group delay

Low differential group delay (DGD) between the modes of a graded-index few-mode fiber is obtained by combining segments with DGD of opposite sign. Transmission of mode-multiplexed 620-GBd QPSK over a record distance of 1200 km is demonstrated.

Sampe Rates, Oscilloscopes

Enhanced Sample Rate, combined with the low-noise system architecture and the tailored brick-wall frequency response in the HDO4000A, HDO6000A, HDO8000A and MDA800A series oscilloscopes dramatically improves the measurement precision when the input frequency signals are very high frequency, such as a high-frequency sine wave or fast edge.

Machine vision, Photometric stereo

Objects with unique 3D aspects can make identifying surface defects with standard machine vision configurations more difficult. One solution to achieve feature-appropriate surface contrast is Photometric Stereo.

Crosstalk Noise, Jitter, Channel Loss

This paper addresses a new methodology for 12 Gbps interoperability that combines a concerted family of pathological channels, internal eye monitoring, and external EQ simulation tools, providing insight into an EQ optimization strategy that addresses the specific channel’s mix of crosstalk noise, jitter, and channel loss. This also provides a backplane designer the ability to configure a high-loss, crosstalk aggressed system.

5G RANs, Performance testing

5G deployments are now underway across the globe but are merely the first steps in a multi-year journey for the mobile industry. Many practical challenges still remain, not least of which is the challenge of cost-effectively deploying 5G Radio Access Networks (RANs) at scale and assuring the performance of supported 5G services.

The 5G RAN architecture provides an open, virtual, packet-based network that extendsfrom the core to the radio antenna. The virtual architecture of 5G RAN with network slicing and new functional elements, such as the Central Unit (CU) and Distributed Unit (DU), enables multiple demanding services to share the same infrastructure without compromising on their specific performance requirements. Virtual, packet-based RANs also enable network sharing over open interfaces as well as multi-vendor implementations, both of which are important to the 5G business case.

Hardware appliances, such as the Remote Radio Head and Baseband Unit of 4G LTE are now replaced with virtual software running on whitebox or Commercial Off-The-Shelf (COTS) hardware. In 5G, the Baseband Unit is split into two new functions, namely the CU and DU. Both these functions can be located either close to the 5G core or close to the Radio Unit (RU) to meet latency and backhaul requirements. This leads to a much more dynamic fronthaul, midhaul and backhaul network, which is now collectively referred to as the 5G cross-haul or “X-haul” network.

It also means that the traditional aggregation architecture where higher capacity is required closer to the core is no longer the norm. As cloud computing and other real-time services move closer to the edge of the network, more traffic is likely to remain close to the subscriber requiring higher capacity X-haul networks with 10G, 25G and even 100G Ethernet connectivity.

The flexibility and dynamic nature of 5G RANs poses new challenges for mobile solution vendors, network operators and service providers. One of those challenges is assuring performance in a highly dynamic environment. Traditional functional, application, integration and protocol testing can be used to test whether 5G equipment is implemented properly and performs as expected. However, these tests are not designed to determine how resilient or robust the equipment will be in the face of network issues that are common in Ethernet networks. 5G RAN packet networks are dynamic with many network configuration possibilities that can change instantaneously. There is, therefore, an additional need to test the limits of network equipment performance under various conditions to ensure dynamic changes in the Ethernet packet network do not lead to service performance issues or outages.

In other words, there is a need to plot the “performance landscape” of the 5G RAN, contouring the performance limits of network equipment and software functions and the 5G RAN itself. Network emulation of the Ethernet-based 5G RAN packet network with impairment testing can be used to stress test network equipment and virtual software in various configurations. This enables vendors to assure performance of their network equipment and software before delivery to network operators. It also enables network operators and service providers to plot their 5G RAN performance landscape at a fraction of the current cost and time and with greater accuracy. This is because testing can now be performed in the lab where a broad variety of scenarios can be tested that are often difficult, if not impossible, to perform in the field.


We experimentally demonstrate transmission of 6 mode-multiplexed 20-Gbd-QPSK signals over 1200 km of three-core microstructured fiber (3C-MSF). An aggregate single-wavelength capacity of 240 Gbit/s is recovered by off-line 66 coherent multiple-input multiple-output (MIMO) digital signal processing.

Oscilloscopes, Signal Analysis

The oscilloscope has been a primary tool for electronic design engineers since the invention of that instrument, many years ago. The first decades of oscilloscopes were “analog” in nature.

We present a novel low-loss 3-spot mode coupler to selectively address 6 spatial and polarization modes of a few-mode fiber. The coupler is used in a 66 MIMO-transmission experiment over a 154-km hybrid span consisting of 129-km depressed-cladding and 25-km graded-index few-mode fiber.


Technologies and design considerations are presented for the design of very high bandwidth oscilloscopes. These include chip, DSP and microwave technologies employed in some of the fastest waveform digitizers in the world.


We experimentally demonstrate 8 dB of mode-equalized distributed Raman gain using a backward pumping scheme. The equivalent noise figure of the amplifier is -1.5 dB, and the amplifier was successfully employed to demonstrate 6-channel mode-multiplexed MIMO transmission over 137-km few-mode fiber.

We experimentally demonstrate multiple-input-multiple-output transmission of a combined 3-space-, and 2-polarization-, and 5-wavelength-division multiplex in a 3-core microstructured fiber over 4200 km. This is the record transmission distance for spatial-division multiplexing in a fiber.

S-Parameters, Continuous Frequency Responses

We explore in detail the relationship between discrete-frequency responses connected with sparameters and the implied continuous time response. This is done in both the frequency- and time-domain to develop the proper insight and explore issues with real time-domain responses, time-aliasing, causality, interpolation and re-sampling of discrete-frequency data. Using the insight gained, we identify the conditions for sufficiency of sampling and the side-effects of the invariable practical conditions when these side-effects cannot be completely dispelled. This paper is especially useful for understanding issues involved in direct application of sparameters in linear simulations, like those used in virtual probing applications in scopes.

Digital Signal Processing

We transmit 32 WDM channels over 12 spatial and polarization modes of 177 km few-mode fiber at a record spectral efficiency of 32 bit/s/Hz. The transmitted signals are strongly coupled and recovered using 12 x 12 multiple-input multiple-output digital signal processing.

Ethernet, SD-WAN

SD-WAN was first introduced to provide a reliable and cost-effective backup to MPLS-based enterprise WAN connectivity. As IP and Internet networks have become more reliable, along with the growth in adoption of cloud services, SD-WAN has evolved and is replacing branch office routers as the preferred WAN connectivity solution.

According to Gartner, 60% of enterprises will have implemented SD-WAN by 2024 compared to just 30% today. At least 30% of enterprise locations will only have Internet WAN connectivity, which is twice the current number. The impact of SD-WAN on the WAN infrastructure market is also clear with Gartner expecting a Compound Annual Growth Rate (CAGR) of -3.1% from 2017 to 2024 as cheaper SD-WAN solutions replace more expensive branch office routers

Nevertheless, one should not make the mistake of thinking that SD-WAN is less complex or intelligent. Quite the contrary in fact. The latest generation of SD-WAN solutions are expected to be application-aware and capable of determining the optimal path through the WAN in real-time on a per application basis. This includes cloud services with direct offload from the branch to co-located cloud edge services. In addition, sophisticated security capabilities are provided to support Zero Trust Network (ZTNA) and/or Secure Access Service Edge (SASE) concepts.

The sophistication of modern SD-WAN solutions allows a true de-coupling of WAN connectivity from the underlying transport mechanism, which is predominantly Ethernet based. It also means that there is little insight into the data transport layer, only to the tunneled SD-WAN connections that are supported. As data consumption continues to grow and more sophisticated and demanding Internet-based services contend for public Internet resources, the underlying data transport layer networks supporting SD-WAN are becoming more dynamic and unpredictable. Multiple choices can be available, such as fixed broadband access over copper or fiber, Fixed Wireless Access (FWA) or 5G mobile broadband, but when should one choose these options, and can one be sure that the current measured performance will be maintained?

Testing sophisticated SD-WAN appliances, virtual functions and services becomes challenging when the SD-WAN solution is intelligent, and the underlying data transport connectivity is dynamic and unpredictable. To ensure that SD-WAN solutions are resilient and robust in the face of unpredictable Ethernet-based network behavior, it is necessary to emulate potential network issues and verify that performance measurement capabilities and SD-WAN policies react appropriately.

Ethernet impairment testing can be used to emulate the underlying Ethernet-based data transport network and introduce errors, otherwise known as impairments, such as packet loss, latency, jitter and packet re-ordering that are likely to occur in dynamic public Internet networks. This technique can be used to create a “performance landscape” where the contours of performance limits can be plotted and understood.

Plotting the SD-WAN performance landscape can help improve the algorithms supporting intelligence in SD-WAN edge appliances and virtual functions as well as the policies and orchestration solutions used to control SD-WAN networks. It can form the basis for Service Level Agreements (SLAs) and it can be used to reproduce WAN connectivity issues that are difficult to resolve.

In short, plotting the performance landscape provides reassurance that the SD-WAN solution will work, no matter what.

Quality Assurance Testing

Companies manufacturing all sorts of products use Quality assurance (QA) to prevent errors and mistakes in their products and ensure flawless product deliveries to their customers. This willimprovecustomer satisfaction and reducethe need for after-salestroubleshooting and support.

QA give companies get a systematic process to find outif their products meet what is required. QA defines requirements for developing and manufacturing reliable products.A driving force behind QA is the ISO(International Organization for Standardization). ISOhas developed the ISO 9000international standard, on which many companies base their QA system.

QA testing is done during and after development andprovidesinformationtodevelopers if changes or improvements are required.During product development the development team will do thorough testing of the product, covering e.g. functional and stress testing of the basic functionality of the product. QA testing of physical products normally includes stress testing of a number of environmental conditions.QA tests that may be conducted include:

  • EMC Tests •Mechanical Tests
  • Thermal/Humidity Tests
  • Hi-Pot Tests
  • Sand and Dust Tests
  • Salt Spray Tests

Medical Devices, Cooling Solutions

The term “Medical Device” covers an expansive range of applications ranging from large MRI machines to hand-held surgical devices and diagnostic tools. These pieces of hardware can be orders of magnitude different in size and power output, so it stands to reason that there is no ‘one size fits all’ cooling solution that is suitable for all medical devices. Learn more about thermal considerations for your next design build or your design iteration of an existing program.

Terabit Ethernet

Networking devices supporting 800Gbps Ethernet are now being developed, with some industry analysts predicting the next tech cycle of 1.6Tbps (Terabits per second) could arrive as early as 2024.

But the devil's in the details - and there are a lot of details.

Xena's new White Paper examines the technical options and challenges of bringing terabit Ethernet to life. Learn how faster electrical lane speeds, new modulation schemes and the need for better Forward Error Correction (FEC) mechanisms are playing a key role, as well as why you'll need to test changes to the Ethernet physical layer and transceiver form factors.


Xena is proud to launch "Freya", our newest and fastest Valkyrie test module. The first of a new product family based on 112Gbps PAM4 SerDes, Freya is aimed at first movers in the 800GE space and designed for 800G switch, transceiver and PHY design validation & Quality Assurance.


A single-polarization 160-Gb/s (80-Gbaud) electronically time-division-multiplexed (ETDM) quadrature phase-shift-keyed (QPSK) signal is generated and coherently detected using two 45-GHz-bandwidth oscilloscope prototypes and offline processing.

Multiplexed Transmissions

We demonstrate 12 x 12 multiple-input multiple-output mode multiplexed transmission over 130-km of few-mode fiber of a combined 6-space-, 2-polarization-, and 8-wavelength-division multiplex, using low-loss photonic lantern and 3D-waveguide mode multiplexers.