The UK telecoms regulator Ofcom has set out new proposals to weaken the hold of BT on the business broadband market.New measures announced by Ofcom on Friday will force BT to give competitors physical access to its 'dark fibre' network of fibre-optic cables and to provide minimum service levels for the broadband connections it provides for rivals too.The fibre-optic proposals will allow other operators that rely on BT's network, such as TalkTalk and Sky, to take direct control of the connection with their own equipment rather than just using BT's.Ofcom said the measures, which are subject to consultation that closes on 31 July this year and should be finalised by mid-2016, are designed to promote competition and innovation in the £2bn market for 'leased lines' - dedicated, high-speed data links that currently run on BT's fibre-optic cables and with its network equipment, which it sells to competitors at regulated prices.Take-up of leased lines is growing due to soaring data usage on smartphones, tablets, and connected TVs, together with the increasingly huge corporate intranet usage to support more sophisticated front-end online services.BT's rivals will now be able to use their own network equipment on the dark fibre network rather than rely on BT's.Ofcom expects this to allow competitors more of an opportunity to create "tailored, high-capacity data links at cost-effective prices" for their customers.As part of its Business Connectivity Market Review, Ofcom is also proposing to place new, minimum quality of service performance requirements on Openreach, the BT unit that installs and maintains connections for competitors using its network."Ofcom is concerned that Openreach often takes too long to install leased lines, and too often changes the date on which it promises to deliver services."Since 2011, the regulator found that the average time between a customer's order and the line being ready had increased from 40 to 46 working days and that it only completed around half of leased line installations on the initial date it promised to its customer.Ofcom expects to publish its final decisions in the first quarter of 2016, taking effect in April 2016, with BT required to publish a draft offer for the industry on dark fibre, containing wholesale pricing and terms for access, in mid-2016."This would then be subject to negotiation between BT and other providers, with a view to BT publishing a final reference offer before the end of 2016. Dark fibre access would then be available to telecoms providers from April 2017."